diff --git a/lib/Doctrine/DBAL/LockMode.php b/lib/Doctrine/DBAL/LockMode.php
new file mode 100644
index 000000000..949072166
--- /dev/null
+++ b/lib/Doctrine/DBAL/LockMode.php
@@ -0,0 +1,42 @@
+<?php
+/*
+ *  $Id$
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * This software consists of voluntary contributions made by many individuals
+ * and is licensed under the LGPL. For more information, see
+ * <http://www.doctrine-project.org>.
+*/
+
+namespace Doctrine\DBAL;
+
+/**
+ * Contains all ORM LockModes
+ *
+ * @license     http://www.opensource.org/licenses/lgpl-license.php LGPL
+ * @link        www.doctrine-project.com
+ * @since       1.0
+ * @version     $Revision$
+ * @author      Benjamin Eberlei <kontakt@beberlei.de>
+ * @author      Roman Borschel <roman@code-factory.org>
+ */
+class LockMode
+{
+    const NONE = 0;
+    const OPTIMISTIC = 1;
+    const PESSIMISTIC_READ = 2;
+    const PESSIMISTIC_WRITE = 4;
+
+    final private function __construct() { }
+}
\ No newline at end of file
diff --git a/lib/Doctrine/DBAL/Platforms/AbstractPlatform.php b/lib/Doctrine/DBAL/Platforms/AbstractPlatform.php
index 87b26f3c6..2bcb7d0ed 100644
--- a/lib/Doctrine/DBAL/Platforms/AbstractPlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/AbstractPlatform.php
@@ -488,11 +488,48 @@ abstract class AbstractPlatform
         return 'COS(' . $value . ')';
     }
 
-    public function getForUpdateSql()
+    public function getForUpdateSQL()
     {
         return 'FOR UPDATE';
     }
 
+    /**
+     * Honors that some SQL vendors such as MsSql use table hints for locking instead of the ANSI SQL FOR UPDATE specification.
+     *
+     * @param  string $fromClause
+     * @param  int $lockMode
+     * @return string
+     */
+    public function appendLockHint($fromClause, $lockMode)
+    {
+        return $fromClause;
+    }
+
+    /**
+     * Get the sql snippet to append to any SELECT statement which locks rows in shared read lock.
+     *
+     * This defaults to the ASNI SQL "FOR UPDATE", which is an exclusive lock (Write). Some database
+     * vendors allow to lighten this constraint up to be a real read lock.
+     *
+     * @return string
+     */
+    public function getReadLockSQL()
+    {
+        return $this->getForUpdateSQL();
+    }
+
+    /**
+     * Get the SQL snippet to append to any SELECT statement which obtains an exclusive lock on the rows.
+     *
+     * The semantics of this lock mode should equal the SELECT .. FOR UPDATE of the ASNI SQL standard.
+     *
+     * @return string
+     */
+    public function getWriteLockSQL()
+    {
+        return $this->getForUpdateSQL();
+    }
+
     public function getDropDatabaseSQL($database)
     {
         return 'DROP DATABASE ' . $database;
diff --git a/lib/Doctrine/DBAL/Platforms/DB2Platform.php b/lib/Doctrine/DBAL/Platforms/DB2Platform.php
index 9cc04840d..6b5072f2a 100644
--- a/lib/Doctrine/DBAL/Platforms/DB2Platform.php
+++ b/lib/Doctrine/DBAL/Platforms/DB2Platform.php
@@ -513,4 +513,9 @@ class DB2Platform extends AbstractPlatform
     {
         return strtoupper($column);
     }
+
+    public function getForUpdateSQL()
+    {
+        return ' WITH RR USE AND KEEP UPDATE LOCKS';
+    }
 }
\ No newline at end of file
diff --git a/lib/Doctrine/DBAL/Platforms/MsSqlPlatform.php b/lib/Doctrine/DBAL/Platforms/MsSqlPlatform.php
index dd14bd8fd..4421c170c 100644
--- a/lib/Doctrine/DBAL/Platforms/MsSqlPlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/MsSqlPlatform.php
@@ -483,4 +483,32 @@ class MsSqlPlatform extends AbstractPlatform
     {
         return 'TRUNCATE TABLE '.$tableName;
     }
+
+    /**
+     * MsSql uses Table Hints for locking strategies instead of the ANSI SQL FOR UPDATE like hints.
+     *
+     * @return string
+     */
+    public function getForUpdateSQL()
+    {
+        return '';
+    }
+
+    /**
+     * @license LGPL
+     * @author Hibernate
+     * @param  string $fromClause
+     * @param  int $lockMode
+     * @return string
+     */
+    public function appendLockHint($fromClause, $lockMode)
+    {
+        if ($lockMode == \Doctrine\DBAL\LockMode::PESSIMISTIC_WRITE) {
+            return $fromClause . " WITH (UPDLOCK, ROWLOCK)";
+        } else if ( $lockMode == \Doctrine\DBAL\LockMode::PESSIMISTIC_READ ) {
+            return $fromClause . " WITH (HOLDLOCK, ROWLOCK)";
+        } else {
+            return $fromClause;
+        }
+    }
 }
diff --git a/lib/Doctrine/DBAL/Platforms/MySqlPlatform.php b/lib/Doctrine/DBAL/Platforms/MySqlPlatform.php
index c7793de95..358a3df70 100644
--- a/lib/Doctrine/DBAL/Platforms/MySqlPlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/MySqlPlatform.php
@@ -583,4 +583,9 @@ class MySqlPlatform extends AbstractPlatform
     {
         return true;
     }
+
+    public function getReadLockSQL()
+    {
+        return 'LOCK IN SHARE MODE';
+    }
 }
diff --git a/lib/Doctrine/DBAL/Platforms/PostgreSqlPlatform.php b/lib/Doctrine/DBAL/Platforms/PostgreSqlPlatform.php
index 972ddc50a..f57c8e85a 100644
--- a/lib/Doctrine/DBAL/Platforms/PostgreSqlPlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/PostgreSqlPlatform.php
@@ -637,4 +637,9 @@ class PostgreSqlPlatform extends AbstractPlatform
     {
         return 'TRUNCATE '.$tableName.' '.($cascade)?'CASCADE':'';
     }
+
+    public function getReadLockSQL()
+    {
+        return 'FOR SHARE';
+    }
 }
diff --git a/lib/Doctrine/DBAL/Platforms/SqlitePlatform.php b/lib/Doctrine/DBAL/Platforms/SqlitePlatform.php
index a1c2184b9..8b209fa60 100644
--- a/lib/Doctrine/DBAL/Platforms/SqlitePlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/SqlitePlatform.php
@@ -428,4 +428,9 @@ class SqlitePlatform extends AbstractPlatform
         }
         return 0;
     }
+
+    public function getForUpdateSql()
+    {
+        return '';
+    }
 }
diff --git a/lib/Doctrine/ORM/EntityManager.php b/lib/Doctrine/ORM/EntityManager.php
index e5ce854ae..a423bcdd1 100644
--- a/lib/Doctrine/ORM/EntityManager.php
+++ b/lib/Doctrine/ORM/EntityManager.php
@@ -318,11 +318,13 @@ class EntityManager
      *
      * @param string $entityName
      * @param mixed $identifier
+     * @param int $lockMode
+     * @param int $lockVersion
      * @return object
      */
-    public function find($entityName, $identifier)
+    public function find($entityName, $identifier, $lockMode = LockMode::NONE, $lockVersion = null)
     {
-        return $this->getRepository($entityName)->find($identifier);
+        return $this->getRepository($entityName)->find($identifier, $lockMode, $lockVersion);
     }
 
     /**
@@ -478,6 +480,20 @@ class EntityManager
         throw new \BadMethodCallException("Not implemented.");
     }
 
+    /**
+     * Acquire a lock on the given entity.
+     *
+     * @param object $entity
+     * @param int $lockMode
+     * @param int $lockVersion
+     * @throws OptimisticLockException
+     * @throws PessimisticLockException
+     */
+    public function lock($entity, $lockMode, $lockVersion = null)
+    {
+        $this->_unitOfWork->lock($entity, $lockMode, $lockVersion);
+    }
+
     /**
      * Gets the repository for an entity class.
      *
diff --git a/lib/Doctrine/ORM/EntityRepository.php b/lib/Doctrine/ORM/EntityRepository.php
index 67eda3a47..d979792f4 100644
--- a/lib/Doctrine/ORM/EntityRepository.php
+++ b/lib/Doctrine/ORM/EntityRepository.php
@@ -87,23 +87,45 @@ class EntityRepository
      * Finds an entity by its primary key / identifier.
      *
      * @param $id The identifier.
-     * @param int $hydrationMode The hydration mode to use.
+     * @param int $lockMode
+     * @param int $lockVersion
      * @return object The entity.
      */
-    public function find($id)
+    public function find($id, $lockMode = LockMode::NONE, $lockVersion = null)
     {
         // Check identity map first
         if ($entity = $this->_em->getUnitOfWork()->tryGetById($id, $this->_class->rootEntityName)) {
+            if ($lockMode != LockMode::NONE) {
+                $this->_em->lock($entity, $lockMode, $lockVersion);
+            }
+
             return $entity; // Hit!
         }
 
         if ( ! is_array($id) || count($id) <= 1) {
-            //FIXME: Not correct. Relies on specific order.
+            // @todo FIXME: Not correct. Relies on specific order.
             $value = is_array($id) ? array_values($id) : array($id);
             $id = array_combine($this->_class->identifier, $value);
         }
 
-        return $this->_em->getUnitOfWork()->getEntityPersister($this->_entityName)->load($id);
+        if ($lockMode == LockMode::NONE) {
+            return $this->_em->getUnitOfWork()->getEntityPersister($this->_entityName)->load($id);
+        } else if ($lockMode == LockMode::OPTIMISTIC) {
+            if (!$this->_class->isVersioned) {
+                throw OptimisticLockException::notVersioned($this->_entityName);
+            }
+            $entity = $this->_em->getUnitOfWork()->getEntityPersister($this->_entityName)->load($id);
+
+            $this->_em->getUnitOfWork()->lock($entity, $lockMode, $lockVersion);
+
+            return $entity;
+        } else {
+            if (!$this->_em->getConnection()->isTransactionActive()) {
+                throw TransactionRequiredException::transactionRequired();
+            }
+            
+            return $this->_em->getUnitOfWork()->getEntityPersister($this->_entityName)->load($id, null, null, array(), $lockMode);
+        }
     }
 
     /**
diff --git a/lib/Doctrine/ORM/LockMode.php b/lib/Doctrine/ORM/LockMode.php
new file mode 100644
index 000000000..45f999a30
--- /dev/null
+++ b/lib/Doctrine/ORM/LockMode.php
@@ -0,0 +1,37 @@
+<?php
+/*
+ *  $Id$
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * This software consists of voluntary contributions made by many individuals
+ * and is licensed under the LGPL. For more information, see
+ * <http://www.doctrine-project.org>.
+*/
+
+namespace Doctrine\ORM;
+
+/**
+ * Contains all ORM LockModes
+ *
+ * @license     http://www.opensource.org/licenses/lgpl-license.php LGPL
+ * @link        www.doctrine-project.com
+ * @since       1.0
+ * @version     $Revision$
+ * @author      Benjamin Eberlei <kontakt@beberlei.de>
+ * @author      Roman Borschel <roman@code-factory.org>
+ */
+class LockMode extends \Doctrine\DBAL\LockMode
+{
+    
+}
\ No newline at end of file
diff --git a/lib/Doctrine/ORM/OptimisticLockException.php b/lib/Doctrine/ORM/OptimisticLockException.php
index 15dd61c44..028698cd8 100644
--- a/lib/Doctrine/ORM/OptimisticLockException.php
+++ b/lib/Doctrine/ORM/OptimisticLockException.php
@@ -24,6 +24,7 @@ namespace Doctrine\ORM;
  * that uses optimistic locking through a version field fails.
  *
  * @author Roman Borschel <roman@code-factory.org>
+ * @author Benjamin Eberlei <kontakt@beberlei.de>
  * @since 2.0
  */
 class OptimisticLockException extends ORMException
@@ -49,4 +50,14 @@ class OptimisticLockException extends ORMException
     {
         return new self("The optimistic lock on an entity failed.", $entity);
     }
+
+    public static function lockFailedVersionMissmatch($entity, $expectedLockVersion, $actualLockVersion)
+    {
+        return new self("The optimistic lock failed, version " . $expectedLockVersion . " was expected, but is actually ".$actualLockVersion, $entity);
+    }
+
+    public static function notVersioned($entityName)
+    {
+        return new self("Cannot obtain optimistic lock on unversioned entity " . $entityName, null);
+    }
 }
\ No newline at end of file
diff --git a/lib/Doctrine/ORM/Persisters/BasicEntityPersister.php b/lib/Doctrine/ORM/Persisters/BasicEntityPersister.php
index 376572b30..0e21f6da5 100644
--- a/lib/Doctrine/ORM/Persisters/BasicEntityPersister.php
+++ b/lib/Doctrine/ORM/Persisters/BasicEntityPersister.php
@@ -482,12 +482,13 @@ class BasicEntityPersister
      *        a new entity is created.
      * @param $assoc The association that connects the entity to load to another entity, if any.
      * @param array $hints Hints for entity creation.
+     * @param int $lockMode
      * @return object The loaded and managed entity instance or NULL if the entity can not be found.
      * @todo Check identity map? loadById method? Try to guess whether $criteria is the id?
      */
-    public function load(array $criteria, $entity = null, $assoc = null, array $hints = array())
+    public function load(array $criteria, $entity = null, $assoc = null, array $hints = array(), $lockMode = 0)
     {
-        $sql = $this->_getSelectEntitiesSQL($criteria, $assoc);
+        $sql = $this->_getSelectEntitiesSQL($criteria, $assoc, $lockMode);
         $stmt = $this->_conn->executeQuery($sql, array_values($criteria));
         $result = $stmt->fetch(PDO::FETCH_ASSOC);
         $stmt->closeCursor();
@@ -772,10 +773,12 @@ class BasicEntityPersister
      *
      * @param array $criteria
      * @param AssociationMapping $assoc
+     * @param string $orderBy
+     * @param int $lockMode
      * @return string
      * @todo Refactor: _getSelectSQL(...)
      */
-    protected function _getSelectEntitiesSQL(array $criteria, $assoc = null)
+    protected function _getSelectEntitiesSQL(array $criteria, $assoc = null, $lockMode = 0)
     {
         $joinSql = $assoc != null && $assoc->isManyToMany() ?
                 $this->_getSelectManyToManyJoinSQL($assoc) : '';
@@ -786,12 +789,20 @@ class BasicEntityPersister
                 $this->_getCollectionOrderBySQL($assoc->orderBy, $this->_getSQLTableAlias($this->_class->name))
                 : '';
 
+        $lockSql = '';
+        if ($lockMode == \Doctrine\ORM\LockMode::PESSIMISTIC_READ) {
+            $lockSql = ' ' . $this->_platform->getReadLockSql();
+        } else if ($lockMode == \Doctrine\ORM\LockMode::PESSIMISTIC_WRITE) {
+            $lockSql = ' ' . $this->_platform->getWriteLockSql();
+        }
+
         return 'SELECT ' . $this->_getSelectColumnListSQL() 
              . ' FROM ' . $this->_class->getQuotedTableName($this->_platform) . ' '
              . $this->_getSQLTableAlias($this->_class->name)
              . $joinSql
              . ($conditionSql ? ' WHERE ' . $conditionSql : '')
-             . $orderBySql;
+             . $orderBySql 
+             . $lockSql;
     }
 
     /**
@@ -1006,6 +1017,30 @@ class BasicEntityPersister
         return $tableAlias;
     }
 
+    /**
+     * Lock all rows of this entity matching the given criteria with the specified pessimistic lock mode
+     *
+     * @param array $criteria
+     * @param int $lockMode
+     * @return void
+     */
+    public function lock(array $criteria, $lockMode)
+    {
+        $conditionSql = $this->_getSelectConditionSQL($criteria);
+
+        if ($lockMode == \Doctrine\ORM\LockMode::PESSIMISTIC_READ) {
+            $lockSql = $this->_platform->getReadLockSql();
+        } else if ($lockMode == \Doctrine\ORM\LockMode::PESSIMISTIC_WRITE) {
+            $lockSql = $this->_platform->getWriteLockSql();
+        }
+
+        $sql = 'SELECT 1 FROM ' . $this->_class->getQuotedTableName($this->_platform) . ' '
+             . $this->_getSQLTableAlias($this->_class->name)
+             . ($conditionSql ? ' WHERE ' . $conditionSql : '') . ' ' . $lockSql;
+        $params = array_values($criteria);
+        $this->_conn->executeQuery($sql, $params);
+    }
+
     /**
      * Gets the conditional SQL fragment used in the WHERE clause when selecting
      * entities in this persister.
@@ -1043,7 +1078,6 @@ class BasicEntityPersister
             }
             $conditionSql .= ' = ?';
         }
-
         return $conditionSql;
     }
 
diff --git a/lib/Doctrine/ORM/Persisters/JoinedSubclassPersister.php b/lib/Doctrine/ORM/Persisters/JoinedSubclassPersister.php
index fd3f9097b..7fb0ead64 100644
--- a/lib/Doctrine/ORM/Persisters/JoinedSubclassPersister.php
+++ b/lib/Doctrine/ORM/Persisters/JoinedSubclassPersister.php
@@ -228,7 +228,7 @@ class JoinedSubclassPersister extends AbstractEntityInheritancePersister
     /**
      * {@inheritdoc}
      */
-    protected function _getSelectEntitiesSQL(array $criteria, $assoc = null)
+    protected function _getSelectEntitiesSQL(array $criteria, $assoc = null, $lockMode = 0)
     {
         $idColumns = $this->_class->getIdentifierColumnNames();
         $baseTableAlias = $this->_getSQLTableAlias($this->_class->name);
@@ -345,6 +345,18 @@ class JoinedSubclassPersister extends AbstractEntityInheritancePersister
                 . $joinSql
                 . ($conditionSql != '' ? ' WHERE ' . $conditionSql : '') . $orderBySql;
     }
+
+    /**
+     * Lock all rows of this entity matching the given criteria with the specified pessimistic lock mode
+     *
+     * @param array $criteria
+     * @param int $lockMode
+     * @return void
+     */
+    public function lock(array $criteria, $lockMode)
+    {
+        throw new \BadMethodCallException("lock() is not yet supported for JoinedSubclassPersister");
+    }
     
     /* Ensure this method is never called. This persister overrides _getSelectEntitiesSQL directly. */
     protected function _getSelectColumnListSQL()
diff --git a/lib/Doctrine/ORM/PessimisticLockException.php b/lib/Doctrine/ORM/PessimisticLockException.php
new file mode 100644
index 000000000..928ead765
--- /dev/null
+++ b/lib/Doctrine/ORM/PessimisticLockException.php
@@ -0,0 +1,40 @@
+<?php
+/*
+ *  $Id$
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * This software consists of voluntary contributions made by many individuals
+ * and is licensed under the LGPL. For more information, see
+ * <http://www.doctrine-project.org>.
+*/
+
+namespace Doctrine\ORM;
+
+/**
+ * Pessimistic Lock Exception
+ *
+ * @license     http://www.opensource.org/licenses/lgpl-license.php LGPL
+ * @link        www.doctrine-project.com
+ * @since       1.0
+ * @version     $Revision$
+ * @author      Benjamin Eberlei <kontakt@beberlei.de>
+ * @author      Roman Borschel <roman@code-factory.org>
+ */
+class PessimisticLockException extends ORMException
+{
+    public static function lockFailed()
+    {
+        return new self("The pessimistic lock failed.");
+    }
+}
\ No newline at end of file
diff --git a/lib/Doctrine/ORM/Query.php b/lib/Doctrine/ORM/Query.php
index b49f9489f..1619aebd2 100644
--- a/lib/Doctrine/ORM/Query.php
+++ b/lib/Doctrine/ORM/Query.php
@@ -93,6 +93,11 @@ final class Query extends AbstractQuery
      */
     const HINT_INTERNAL_ITERATION = 'doctrine.internal.iteration';
 
+    /**
+     * @var string
+     */
+    const HINT_LOCK_MODE = 'doctrine.lockMode';
+
     /**
      * @var integer $_state   The current state of this query.
      */
@@ -487,6 +492,39 @@ final class Query extends AbstractQuery
         return parent::setHydrationMode($hydrationMode);
     }
 
+    /**
+     * Set the lock mode for this Query.
+     *
+     * @see Doctrine\ORM\LockMode
+     * @param  int $lockMode
+     * @return Query
+     */
+    public function setLockMode($lockMode)
+    {
+        if ($lockMode == LockMode::PESSIMISTIC_READ || $lockMode == LockMode::PESSIMISTIC_WRITE) {
+            if (!$this->_em->getConnection()->isTransactionActive()) {
+                throw TransactionRequiredException::transactionRequired();
+            }
+        }
+
+        $this->setHint(self::HINT_LOCK_MODE, $lockMode);
+        return $this;
+    }
+
+    /**
+     * Get the current lock mode for this query.
+     *
+     * @return int
+     */
+    public function getLockMode()
+    {
+        $lockMode = $this->getHint(self::HINT_LOCK_MODE);
+        if (!$lockMode) {
+            return LockMode::NONE;
+        }
+        return $lockMode;
+    }
+
     /**
      * Generate a cache id for the query cache - reusing the Result-Cache-Id generator.
      *
diff --git a/lib/Doctrine/ORM/Query/SqlWalker.php b/lib/Doctrine/ORM/Query/SqlWalker.php
index 52e73585e..ca445d81f 100644
--- a/lib/Doctrine/ORM/Query/SqlWalker.php
+++ b/lib/Doctrine/ORM/Query/SqlWalker.php
@@ -366,6 +366,25 @@ class SqlWalker implements TreeWalker
             $sql, $this->_query->getMaxResults(), $this->_query->getFirstResult()
         );
 
+        if (($lockMode = $this->_query->getHint(Query::HINT_LOCK_MODE)) !== false) {
+            if ($lockMode == \Doctrine\ORM\LockMode::PESSIMISTIC_READ) {
+                $sql .= " " . $this->_platform->getReadLockSQL();
+            } else if ($lockMode == \Doctrine\ORM\LockMode::PESSIMISTIC_WRITE) {
+                $sql .= " " . $this->_platform->getWriteLockSQL();
+            } else if ($lockMode == \Doctrine\ORM\LockMode::OPTIMISTIC) {
+                $versionedClassFound = false;
+                foreach ($this->_selectedClasses AS $class) {
+                    if ($class->isVersioned) {
+                        $versionedClassFound = true;
+                    }
+                }
+
+                if (!$versionedClassFound) {
+                    throw \Doctrine\ORM\OptimisticLockException::lockFailed();
+                }
+            }
+        }
+
         return $sql;
     }
 
@@ -603,7 +622,7 @@ class SqlWalker implements TreeWalker
             $sql .= $this->walkJoinVariableDeclaration($joinVarDecl);
         }
 
-        return $sql;
+        return $this->_platform->appendLockHint($sql, $this->_query->getHint(Query::HINT_LOCK_MODE));
     }
 
     /**
diff --git a/lib/Doctrine/ORM/TransactionRequiredException.php b/lib/Doctrine/ORM/TransactionRequiredException.php
new file mode 100644
index 000000000..170f63e50
--- /dev/null
+++ b/lib/Doctrine/ORM/TransactionRequiredException.php
@@ -0,0 +1,40 @@
+<?php
+/*
+ *  $Id$
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * This software consists of voluntary contributions made by many individuals
+ * and is licensed under the LGPL. For more information, see
+ * <http://www.doctrine-project.org>.
+*/
+
+namespace Doctrine\ORM;
+
+/**
+ * Is thrown when a transaction is required for the current operation, but there is none open.
+ *
+ * @license     http://www.opensource.org/licenses/lgpl-license.php LGPL
+ * @link        www.doctrine-project.com
+ * @since       1.0
+ * @version     $Revision$
+ * @author      Benjamin Eberlei <kontakt@beberlei.de>
+ * @author      Roman Borschel <roman@code-factory.org>
+ */
+class TransactionRequiredException extends ORMException
+{
+    static public function transactionRequired()
+    {
+        return new self('An open transaction is required for this operation.');
+    }
+}
\ No newline at end of file
diff --git a/lib/Doctrine/ORM/UnitOfWork.php b/lib/Doctrine/ORM/UnitOfWork.php
index 948ee1be2..2428098ef 100644
--- a/lib/Doctrine/ORM/UnitOfWork.php
+++ b/lib/Doctrine/ORM/UnitOfWork.php
@@ -1346,7 +1346,7 @@ class UnitOfWork implements PropertyChangedListener
                 $entityVersion = $class->reflFields[$class->versionField]->getValue($entity);
                 // Throw exception if versions dont match.
                 if ($managedCopyVersion != $entityVersion) {
-                    throw OptimisticLockException::lockFailed($entity);
+                    throw OptimisticLockException::lockFailedVersionMissmatch($entityVersion, $managedCopyVersion);
                 }
             }
 
@@ -1630,6 +1630,48 @@ class UnitOfWork implements PropertyChangedListener
         }
     }
 
+    /**
+     * Acquire a lock on the given entity.
+     *
+     * @param object $entity
+     * @param int $lockMode
+     * @param int $lockVersion
+     */
+    public function lock($entity, $lockMode, $lockVersion = null)
+    {
+        if ($this->getEntityState($entity) != self::STATE_MANAGED) {
+            throw new \InvalidArgumentException("Entity is not MANAGED.");
+        }
+        
+        $entityName = get_class($entity);
+        $class = $this->_em->getClassMetadata($entityName);
+
+        if ($lockMode == LockMode::OPTIMISTIC) {
+            if (!$class->isVersioned) {
+                throw OptimisticLockException::notVersioned($entityName);
+            }
+
+            if ($lockVersion != null) {
+                $entityVersion = $class->reflFields[$class->versionField]->getValue($entity);
+                if ($entityVersion != $lockVersion) {
+                    throw OptimisticLockException::lockFailedVersionMissmatch($entity, $lockVersion, $entityVersion);
+                }
+            }
+        } else if ($lockMode == LockMode::PESSIMISTIC_READ || $lockMode == LockMode::PESSIMISTIC_WRITE) {
+
+            if (!$this->_em->getConnection()->isTransactionActive()) {
+                throw TransactionRequiredException::transactionRequired();
+            }
+            
+            $oid = spl_object_hash($entity);
+
+            $this->getEntityPersister($class->name)->lock(
+                array_combine($class->getIdentifierColumnNames(), $this->_entityIdentifiers[$oid]),
+                $lockMode
+            );
+        }
+    }
+
     /**
      * Gets the CommitOrderCalculator used by the UnitOfWork to order commits.
      *
diff --git a/tests/Doctrine/Tests/Models/CMS/CmsArticle.php b/tests/Doctrine/Tests/Models/CMS/CmsArticle.php
index 1d7901557..222212907 100644
--- a/tests/Doctrine/Tests/Models/CMS/CmsArticle.php
+++ b/tests/Doctrine/Tests/Models/CMS/CmsArticle.php
@@ -31,6 +31,11 @@ class CmsArticle
      * @OneToMany(targetEntity="CmsComment", mappedBy="article")
      */
     public $comments;
+
+    /**
+     * @Version @column(type="integer")
+     */
+    public $version;
     
     public function setAuthor(CmsUser $author) {
         $this->user = $author;
diff --git a/tests/Doctrine/Tests/ORM/Functional/EntityRepositoryTest.php b/tests/Doctrine/Tests/ORM/Functional/EntityRepositoryTest.php
index 856c7b8d2..9bb2253ee 100644
--- a/tests/Doctrine/Tests/ORM/Functional/EntityRepositoryTest.php
+++ b/tests/Doctrine/Tests/ORM/Functional/EntityRepositoryTest.php
@@ -93,5 +93,62 @@ class EntityRepositoryTest extends \Doctrine\Tests\OrmFunctionalTestCase
         $this->_em->getRepository('Doctrine\Tests\Models\CMS\CmsUser')
                   ->findByThisFieldDoesNotExist('testvalue');
     }
+
+    /**
+     * @group locking
+     * @group DDC-178
+     */
+    public function testPessimisticReadLockWithoutTransaction_ThrowsException()
+    {
+        $this->setExpectedException('Doctrine\ORM\TransactionRequiredException');
+
+        $this->_em->getRepository('Doctrine\Tests\Models\CMS\CmsUser')
+                  ->find(1, \Doctrine\ORM\LockMode::PESSIMISTIC_READ);
+    }
+
+    /**
+     * @group locking
+     * @group DDC-178
+     */
+    public function testPessimisticWriteLockWithoutTransaction_ThrowsException()
+    {
+        $this->setExpectedException('Doctrine\ORM\TransactionRequiredException');
+
+        $this->_em->getRepository('Doctrine\Tests\Models\CMS\CmsUser')
+                  ->find(1, \Doctrine\ORM\LockMode::PESSIMISTIC_WRITE);
+    }
+
+    /**
+     * @group locking
+     * @group DDC-178
+     */
+    public function testOptimisticLockUnversionedEntity_ThrowsException()
+    {
+        $this->setExpectedException('Doctrine\ORM\OptimisticLockException');
+
+        $this->_em->getRepository('Doctrine\Tests\Models\CMS\CmsUser')
+                  ->find(1, \Doctrine\ORM\LockMode::OPTIMISTIC);
+    }
+
+    /**
+     * @group locking
+     * @group DDC-178
+     */
+    public function testIdentityMappedOptimisticLockUnversionedEntity_ThrowsException()
+    {
+        $user = new CmsUser;
+        $user->name = 'Roman';
+        $user->username = 'romanb';
+        $user->status = 'freak';
+        $this->_em->persist($user);
+        $this->_em->flush();
+
+        $userId = $user->id;
+
+        $this->_em->find('Doctrine\Tests\Models\Cms\CmsUser', $userId);
+        
+        $this->setExpectedException('Doctrine\ORM\OptimisticLockException');
+        $this->_em->find('Doctrine\Tests\Models\Cms\CmsUser', $userId, \Doctrine\ORM\LockMode::OPTIMISTIC);
+    }
 }
 
diff --git a/tests/Doctrine/Tests/ORM/Functional/Locking/AllTests.php b/tests/Doctrine/Tests/ORM/Functional/Locking/AllTests.php
index 9b021ced8..be725f0b0 100644
--- a/tests/Doctrine/Tests/ORM/Functional/Locking/AllTests.php
+++ b/tests/Doctrine/Tests/ORM/Functional/Locking/AllTests.php
@@ -20,6 +20,7 @@ class AllTests
         $suite = new \Doctrine\Tests\DoctrineTestSuite('Doctrine Orm Functional Locking');
 
         $suite->addTestSuite('Doctrine\Tests\ORM\Functional\Locking\OptimisticTest');
+        $suite->addTestSuite('Doctrine\Tests\ORM\Functional\Locking\LockTest');
 
         return $suite;
     }
diff --git a/tests/Doctrine/Tests/ORM/Functional/Locking/GearmanLockTest.php b/tests/Doctrine/Tests/ORM/Functional/Locking/GearmanLockTest.php
new file mode 100644
index 000000000..0efca5c12
--- /dev/null
+++ b/tests/Doctrine/Tests/ORM/Functional/Locking/GearmanLockTest.php
@@ -0,0 +1,177 @@
+<?php
+
+namespace Doctrine\Tests\ORM\Functional\Locking;
+
+use Doctrine\Tests\Models\CMS\CmsArticle,
+    Doctrine\Tests\Models\CMS\CmsUser,
+    Doctrine\ORM\LockMode,
+    Doctrine\ORM\EntityManager;
+
+require_once __DIR__ . '/../../../TestInit.php';
+
+class GearmanLockTest extends \Doctrine\Tests\OrmFunctionalTestCase
+{
+    private $gearman = null;
+    private $maxRunTime = 0;
+    private $articleId;
+
+    protected function setUp()
+    {
+        if (!class_exists('GearmanClient', false)) {
+            $this->markTestSkipped('pecl/gearman is required for this test to run.');
+        }
+
+        $this->useModelSet('cms');
+        parent::setUp();
+        $this->tasks = array();
+
+        $this->gearman = new \GearmanClient();
+        $this->gearman->addServer();
+        $this->gearman->setCompleteCallback(array($this, "gearmanTaskCompleted"));
+
+        $article = new CmsArticle();
+        $article->text = "my article";
+        $article->topic = "Hello";
+
+        $this->_em->persist($article);
+        $this->_em->flush();
+
+        $this->articleId = $article->id;
+    }
+
+    public function gearmanTaskCompleted($task)
+    {
+        $this->maxRunTime = max($this->maxRunTime, $task->data());
+    }
+
+    public function testFindWithLock()
+    {
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_WRITE);
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_WRITE);
+        
+        $this->assertLockWorked();
+    }
+
+    public function testFindWithWriteThenReadLock()
+    {
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_WRITE);
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_READ);
+
+        $this->assertLockWorked();
+    }
+
+    public function testFindWithReadThenWriteLock()
+    {
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_READ);
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_WRITE);
+
+        $this->assertLockWorked();
+    }
+
+    public function testFindWithOneLock()
+    {
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_WRITE);
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::NONE);
+
+        $this->assertLockDoesNotBlock();
+    }
+
+    public function testDqlWithLock()
+    {
+        $this->asyncDqlWithLock('SELECT a FROM Doctrine\Tests\Models\CMS\CmsArticle a', array(), LockMode::PESSIMISTIC_WRITE);
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_WRITE);
+
+        $this->assertLockWorked();
+    }
+
+    public function testLock()
+    {
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_WRITE);
+        $this->asyncLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_WRITE);
+
+        $this->assertLockWorked();
+    }
+
+    public function testLock2()
+    {
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_WRITE);
+        $this->asyncLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_READ);
+
+        $this->assertLockWorked();
+    }
+
+    public function testLock3()
+    {
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_READ);
+        $this->asyncLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_WRITE);
+
+        $this->assertLockWorked();
+    }
+
+    public function testLock4()
+    {
+        $this->asyncFindWithLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::NONE);
+        $this->asyncLock('Doctrine\Tests\Models\CMS\CmsArticle', $this->articleId, LockMode::PESSIMISTIC_WRITE);
+
+        $this->assertLockDoesNotBlock();
+    }
+
+    protected function assertLockDoesNotBlock()
+    {
+        $this->assertLockWorked($onlyForSeconds = 1);
+    }
+
+    protected function assertLockWorked($forTime = 2, $notLongerThan = null)
+    {
+        if ($notLongerThan === null) {
+            $notLongerThan = $forTime + 1;
+        }
+
+        $this->gearman->runTasks();
+
+        $this->assertTrue($this->maxRunTime > $forTime,
+            "Because of locking this tests should have run at least " . $forTime . " seconds, ".
+            "but only did for " . $this->maxRunTime . " seconds.");
+        $this->assertTrue($this->maxRunTime < $notLongerThan,
+            "The longest task should not run longer than " . $notLongerThan . " seconds, ".
+            "but did for " . $this->maxRunTime . " seconds."
+        );
+    }
+
+    protected function asyncFindWithLock($entityName, $entityId, $lockMode)
+    {
+        $this->startJob('findWithLock', array(
+            'entityName' => $entityName,
+            'entityId' => $entityId,
+            'lockMode' => $lockMode,
+        ));
+    }
+
+    protected function asyncDqlWithLock($dql, $params, $lockMode)
+    {
+        $this->startJob('dqlWithLock', array(
+            'dql' => $dql,
+            'dqlParams' => $params,
+            'lockMode' => $lockMode,
+        ));
+    }
+
+    protected function asyncLock($entityName, $entityId, $lockMode)
+    {
+        $this->startJob('lock', array(
+            'entityName' => $entityName,
+            'entityId' => $entityId,
+            'lockMode' => $lockMode,
+        ));
+    }
+
+    protected function startJob($fn, $fixture)
+    {
+        $this->gearman->addTask($fn, serialize(array(
+            'conn' => $this->_em->getConnection()->getParams(),
+            'fixture' => $fixture
+        )));
+
+        $this->assertEquals(GEARMAN_SUCCESS, $this->gearman->returnCode());
+    }
+}
\ No newline at end of file
diff --git a/tests/Doctrine/Tests/ORM/Functional/Locking/LockAgentWorker.php b/tests/Doctrine/Tests/ORM/Functional/Locking/LockAgentWorker.php
new file mode 100644
index 000000000..146f2db4d
--- /dev/null
+++ b/tests/Doctrine/Tests/ORM/Functional/Locking/LockAgentWorker.php
@@ -0,0 +1,112 @@
+<?php
+
+namespace Doctrine\Tests\ORM\Functional\Locking;
+
+require_once __DIR__ . "/../../../TestInit.php";
+
+class LockAgentWorker
+{
+    private $em;
+
+    static public function run()
+    {
+        $lockAgent = new LockAgentWorker();
+
+        $worker = new \GearmanWorker();
+        $worker->addServer();
+        $worker->addFunction("findWithLock", array($lockAgent, "findWithLock"));
+        $worker->addFunction("dqlWithLock", array($lockAgent, "dqlWithLock"));
+        $worker->addFunction('lock', array($lockAgent, 'lock'));
+
+        while($worker->work()) {
+            if ($worker->returnCode() != GEARMAN_SUCCESS) {
+                echo "return_code: " . $worker->returnCode() . "\n";
+                break;
+            }
+        }
+    }
+
+    protected function process($job, \Closure $do)
+    {
+        $fixture = $this->processWorkload($job);
+
+        $s = microtime(true);
+        $this->em->beginTransaction();
+        $do($fixture, $this->em);
+
+        sleep(1);
+        $this->em->rollback();
+        $this->em->clear();
+        $this->em->close();
+        $this->em->getConnection()->close();
+
+        return (microtime(true) - $s);
+    }
+
+    public function findWithLock($job)
+    {
+        return $this->process($job, function($fixture, $em) {
+            $entity = $em->find($fixture['entityName'], $fixture['entityId'], $fixture['lockMode']);
+        });
+    }
+
+    public function dqlWithLock($job)
+    {
+        return $this->process($job, function($fixture, $em) {
+            /* @var $query Doctrine\ORM\Query */
+            $query = $em->createQuery($fixture['dql']);
+            $query->setLockMode($fixture['lockMode']);
+            $query->setParameters($fixture['dqlParams']);
+            $result = $query->getResult();
+        });
+    }
+
+    public function lock($job)
+    {
+        return $this->process($job, function($fixture, $em) {
+            $entity = $em->find($fixture['entityName'], $fixture['entityId']);
+            $em->lock($entity, $fixture['lockMode']);
+        });
+    }
+
+    protected function processWorkload($job)
+    {
+        echo "Received job: " . $job->handle() . " for function " . $job->functionName() . "\n";
+
+        $workload = $job->workload();
+        $workload = unserialize($workload);
+
+        if (!isset($workload['conn']) || !is_array($workload['conn'])) {
+            throw new \InvalidArgumentException("Missing Database parameters");
+        }
+
+        $this->em = $this->createEntityManager($workload['conn']);
+
+        if (!isset($workload['fixture'])) {
+            throw new \InvalidArgumentException("Missing Fixture parameters");
+        }
+        return $workload['fixture'];
+    }
+
+    protected function createEntityManager($conn)
+    {
+        $config = new \Doctrine\ORM\Configuration();
+        $config->setProxyDir(__DIR__ . '/../../../Proxies');
+        $config->setProxyNamespace('MyProject\Proxies');
+        $config->setAutoGenerateProxyClasses(true);
+
+        $annotDriver = $config->newDefaultAnnotationDriver(array(__DIR__ . '/../../../Models/'));
+        $config->setMetadataDriverImpl($annotDriver);
+
+        $cache = new \Doctrine\Common\Cache\ArrayCache();
+        $config->setMetadataCacheImpl($cache);
+        $config->setQueryCacheImpl($cache);
+        $config->setSQLLogger(new \Doctrine\DBAL\Logging\EchoSQLLogger());
+
+        $em = \Doctrine\ORM\EntityManager::create($conn, $config);
+
+        return $em;
+    }
+}
+
+LockAgentWorker::run();
\ No newline at end of file
diff --git a/tests/Doctrine/Tests/ORM/Functional/Locking/LockTest.php b/tests/Doctrine/Tests/ORM/Functional/Locking/LockTest.php
new file mode 100644
index 000000000..5d0834557
--- /dev/null
+++ b/tests/Doctrine/Tests/ORM/Functional/Locking/LockTest.php
@@ -0,0 +1,157 @@
+<?php
+
+namespace Doctrine\Tests\ORM\Functional\Locking;
+
+use Doctrine\Tests\Models\CMS\CmsArticle,
+    Doctrine\Tests\Models\CMS\CmsUser,
+    Doctrine\ORM\LockMode,
+    Doctrine\ORM\EntityManager;
+
+require_once __DIR__ . '/../../../TestInit.php';
+
+class LockTest extends \Doctrine\Tests\OrmFunctionalTestCase {
+    protected function setUp() {
+        $this->useModelSet('cms');
+        parent::setUp();
+        $this->handles = array();
+    }
+
+    /**
+     * @group DDC-178
+     * @group locking
+     */
+    public function testLockVersionedEntity() {
+        $article = new CmsArticle();
+        $article->text = "my article";
+        $article->topic = "Hello";
+
+        $this->_em->persist($article);
+        $this->_em->flush();
+
+        $this->_em->lock($article, LockMode::OPTIMISTIC, $article->version);
+    }
+
+    /**
+     * @group DDC-178
+     * @group locking
+     */
+    public function testLockVersionedEntity_MissmatchThrowsException() {
+        $article = new CmsArticle();
+        $article->text = "my article";
+        $article->topic = "Hello";
+
+        $this->_em->persist($article);
+        $this->_em->flush();
+
+        $this->setExpectedException('Doctrine\ORM\OptimisticLockException');
+        $this->_em->lock($article, LockMode::OPTIMISTIC, $article->version + 1);
+    }
+
+    /**
+     * @group DDC-178
+     * @group locking
+     */
+    public function testLockUnversionedEntity_ThrowsException() {
+        $user = new CmsUser();
+        $user->name = "foo";
+        $user->status = "active";
+        $user->username = "foo";
+
+        $this->_em->persist($user);
+        $this->_em->flush();
+
+        $this->setExpectedException('Doctrine\ORM\OptimisticLockException');
+        $this->_em->lock($user, LockMode::OPTIMISTIC);
+    }
+
+    /**
+     * @group DDC-178
+     * @group locking
+     */
+    public function testLockUnmanagedEntity_ThrowsException() {
+        $article = new CmsArticle();
+
+        $this->setExpectedException('InvalidArgumentException', 'Entity is not MANAGED.');
+        $this->_em->lock($article, LockMode::OPTIMISTIC, $article->version + 1);
+    }
+
+    /**
+     * @group DDC-178
+     * @group locking
+     */
+    public function testLockPessimisticRead_NoTransaction_ThrowsException() {
+        $article = new CmsArticle();
+        $article->text = "my article";
+        $article->topic = "Hello";
+
+        $this->_em->persist($article);
+        $this->_em->flush();
+
+        $this->setExpectedException('Doctrine\ORM\TransactionRequiredException');
+        $this->_em->lock($article, LockMode::PESSIMISTIC_READ);
+    }
+
+    /**
+     * @group DDC-178
+     * @group locking
+     */
+    public function testLockPessimisticWrite_NoTransaction_ThrowsException() {
+        $article = new CmsArticle();
+        $article->text = "my article";
+        $article->topic = "Hello";
+
+        $this->_em->persist($article);
+        $this->_em->flush();
+
+        $this->setExpectedException('Doctrine\ORM\TransactionRequiredException');
+        $this->_em->lock($article, LockMode::PESSIMISTIC_WRITE);
+    }
+
+    /**
+     * @group DDC-178
+     * @group locking
+     */
+    public function testLockPessimisticWrite() {
+        $writeLockSql = $this->_em->getConnection()->getDatabasePlatform()->getWriteLockSql();
+        if (strlen($writeLockSql) == 0) {
+            $this->markTestSkipped('Database Driver has no Write Lock support.');
+        }
+
+        $article = new CmsArticle();
+        $article->text = "my article";
+        $article->topic = "Hello";
+
+        $this->_em->persist($article);
+        $this->_em->flush();
+
+        $this->_em->beginTransaction();
+        $this->_em->lock($article, LockMode::PESSIMISTIC_WRITE);
+
+        $query = array_pop( $this->_sqlLoggerStack->queries );
+        $this->assertContains($writeLockSql, $query['sql']);
+    }
+
+    /**
+     * @group DDC-178
+     * @group locking
+     */
+    public function testLockPessimisticRead() {
+        $readLockSql = $this->_em->getConnection()->getDatabasePlatform()->getReadLockSql();
+        if (strlen($readLockSql) == 0) {
+            $this->markTestSkipped('Database Driver has no Write Lock support.');
+        }
+
+        $article = new CmsArticle();
+        $article->text = "my article";
+        $article->topic = "Hello";
+
+        $this->_em->persist($article);
+        $this->_em->flush();
+
+        $this->_em->beginTransaction();
+        $this->_em->lock($article, LockMode::PESSIMISTIC_READ);
+
+        $query = array_pop( $this->_sqlLoggerStack->queries );
+        $this->assertContains($readLockSql, $query['sql']);
+    }
+}
\ No newline at end of file
diff --git a/tests/Doctrine/Tests/ORM/Query/SelectSqlGenerationTest.php b/tests/Doctrine/Tests/ORM/Query/SelectSqlGenerationTest.php
index 716182ac1..0b8fc8847 100644
--- a/tests/Doctrine/Tests/ORM/Query/SelectSqlGenerationTest.php
+++ b/tests/Doctrine/Tests/ORM/Query/SelectSqlGenerationTest.php
@@ -15,13 +15,16 @@ class SelectSqlGenerationTest extends \Doctrine\Tests\OrmTestCase
         $this->_em = $this->_getTestEntityManager();
     }
 
-    public function assertSqlGeneration($dqlToBeTested, $sqlToBeConfirmed)
+    public function assertSqlGeneration($dqlToBeTested, $sqlToBeConfirmed, array $queryHints = array())
     {
         try {
             $query = $this->_em->createQuery($dqlToBeTested);
             $query->setHint(Query::HINT_FORCE_PARTIAL_LOAD, true)
                     ->useQueryCache(false);
-
+            
+            foreach ($queryHints AS $name => $value) {
+                $query->setHint($name, $value);
+            }
             parent::assertEquals($sqlToBeConfirmed, $query->getSql());
             $query->free();
         } catch (\Exception $e) {
@@ -57,7 +60,7 @@ class SelectSqlGenerationTest extends \Doctrine\Tests\OrmTestCase
     {
         $this->assertSqlGeneration(
             'SELECT a FROM Doctrine\Tests\Models\CMS\CmsArticle a ORDER BY a.user.name ASC',
-            'SELECT c0_.id AS id0, c0_.topic AS topic1, c0_.text AS text2 FROM cms_articles c0_ INNER JOIN cms_users c1_ ON c0_.user_id = c1_.id ORDER BY c1_.name ASC'
+            'SELECT c0_.id AS id0, c0_.topic AS topic1, c0_.text AS text2, c0_.version AS version3 FROM cms_articles c0_ INNER JOIN cms_users c1_ ON c0_.user_id = c1_.id ORDER BY c1_.name ASC'
         );
     }
 
@@ -181,11 +184,11 @@ class SelectSqlGenerationTest extends \Doctrine\Tests\OrmTestCase
         );
     }
 
-    public function testSupportsMultipleEntitesInFromClause()
+    public function testSupportsMultipleEntitiesInFromClause()
     {
         $this->assertSqlGeneration(
             'SELECT u, a FROM Doctrine\Tests\Models\CMS\CmsUser u, Doctrine\Tests\Models\CMS\CmsArticle a WHERE u.id = a.user.id',
-            'SELECT c0_.id AS id0, c0_.status AS status1, c0_.username AS username2, c0_.name AS name3, c1_.id AS id4, c1_.topic AS topic5, c1_.text AS text6 FROM cms_users c0_ INNER JOIN cms_users c2_ ON c1_.user_id = c2_.id WHERE c0_.id = c2_.id'
+            'SELECT c0_.id AS id0, c0_.status AS status1, c0_.username AS username2, c0_.name AS name3, c1_.id AS id4, c1_.topic AS topic5, c1_.text AS text6, c1_.version AS version7 FROM cms_users c0_ INNER JOIN cms_users c2_ ON c1_.user_id = c2_.id WHERE c0_.id = c2_.id'
         );
     }
 
@@ -587,7 +590,41 @@ class SelectSqlGenerationTest extends \Doctrine\Tests\OrmTestCase
     }
 
     /**
-     * DDC-430
+     * @group locking
+     * @group DDC-178
+     */
+    public function testPessimisticWriteLockQueryHint()
+    {
+        if ($this->_em->getConnection()->getDatabasePlatform() instanceof \Doctrine\DBAL\Platforms\SqlitePlatform) {
+            $this->markTestSkipped('SqLite does not support Row locking at all.');
+        }
+
+        $this->assertSqlGeneration(
+            "SELECT u FROM Doctrine\Tests\Models\CMS\CmsUser u WHERE u.username = 'gblanco'",
+            "SELECT c0_.id AS id0, c0_.status AS status1, c0_.username AS username2, c0_.name AS name3 ".
+            "FROM cms_users c0_ WHERE c0_.username = 'gblanco' FOR UPDATE",
+            array(Query::HINT_LOCK_MODE => \Doctrine\ORM\LockMode::PESSIMISTIC_WRITE)
+        );
+    }
+
+    /**
+     * @group locking
+     * @group DDC-178
+     */
+    public function testPessimisticReadLockQueryHintPostgreSql()
+    {
+        $this->_em->getConnection()->setDatabasePlatform(new \Doctrine\DBAL\Platforms\PostgreSqlPlatform);
+
+        $this->assertSqlGeneration(
+            "SELECT u FROM Doctrine\Tests\Models\CMS\CmsUser u WHERE u.username = 'gblanco'",
+            "SELECT c0_.id AS id0, c0_.status AS status1, c0_.username AS username2, c0_.name AS name3 ".
+            "FROM cms_users c0_ WHERE c0_.username = 'gblanco' FOR SHARE",
+            array(Query::HINT_LOCK_MODE => \Doctrine\ORM\LockMode::PESSIMISTIC_READ)
+                );
+    }
+
+    /**
+     * @group DDC-430
      */
     public function testSupportSelectWithMoreThan10InputParameters()
     {
@@ -598,7 +635,39 @@ class SelectSqlGenerationTest extends \Doctrine\Tests\OrmTestCase
     }
 
     /**
-     * DDC-431
+     * @group locking
+     * @group DDC-178
+     */
+    public function testPessimisticReadLockQueryHintMySql()
+    {
+        $this->_em->getConnection()->setDatabasePlatform(new \Doctrine\DBAL\Platforms\MySqlPlatform);
+
+        $this->assertSqlGeneration(
+            "SELECT u FROM Doctrine\Tests\Models\CMS\CmsUser u WHERE u.username = 'gblanco'",
+            "SELECT c0_.id AS id0, c0_.status AS status1, c0_.username AS username2, c0_.name AS name3 ".
+            "FROM cms_users c0_ WHERE c0_.username = 'gblanco' LOCK IN SHARE MODE",
+            array(Query::HINT_LOCK_MODE => \Doctrine\ORM\LockMode::PESSIMISTIC_READ)
+        );
+    }
+
+    /**
+     * @group locking
+     * @group DDC-178
+     */
+    public function testPessimisticReadLockQueryHintOracle()
+    {
+        $this->_em->getConnection()->setDatabasePlatform(new \Doctrine\DBAL\Platforms\OraclePlatform);
+
+        $this->assertSqlGeneration(
+            "SELECT u FROM Doctrine\Tests\Models\CMS\CmsUser u WHERE u.username = 'gblanco'",
+            "SELECT c0_.id AS id0, c0_.status AS status1, c0_.username AS username2, c0_.name AS name3 ".
+            "FROM cms_users c0_ WHERE c0_.username = 'gblanco' FOR UPDATE",
+            array(Query::HINT_LOCK_MODE => \Doctrine\ORM\LockMode::PESSIMISTIC_READ)
+        );
+    }
+
+    /**
+     * @group DDC-431
      */
     public function testSupportToCustomDQLFunctions()
     {
diff --git a/tests/README.markdown b/tests/README.markdown
new file mode 100644
index 000000000..c1027aced
--- /dev/null
+++ b/tests/README.markdown
@@ -0,0 +1,25 @@
+# Running the Doctrine 2 Testsuite
+
+## Setting up a PHPUnit Configuration XML
+
+..
+
+## Testing Lock-Support
+
+The Lock support in Doctrine 2 is tested using Gearman, which allows to run concurrent tasks in parallel.
+Install Gearman with PHP as follows:
+
+1. Go to http://www.gearman.org and download the latest Gearman Server
+2. Compile it and then call ldconfig
+3. Start it up "gearmand -vvvv"
+4. Install pecl/gearman by calling "gearman-beta"
+
+You can then go into tests/ and start up two workers:
+
+    php Doctrine/Tests/ORM/Functional/Locking/LockAgentWorker.php
+
+Then run the locking test-suite:
+
+    phpunit --configuration <myconfig.xml> Doctrine/Tests/ORM/Functional/Locking/GearmanLockTest.php
+
+This can run considerable time, because it is using sleep() to test for the timing ranges of locks.
\ No newline at end of file