diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 14bd394..7b7b4d4 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -8,10 +8,6 @@
     <includePath>.</includePath>
   </php>
   <logging>
-      <!--
-      <log type="coverage-html" target="build/logs/coverage" lowUpperBound="35"
-       highLowerBound="70"/>
-      -->
       <log type="coverage-clover" target="build/logs/clover.xml"/>
   </logging>
   <filter>
diff --git a/src/DatabaseL2.php b/src/DatabaseL2.php
index 95c4f83..e74176d 100644
--- a/src/DatabaseL2.php
+++ b/src/DatabaseL2.php
@@ -33,7 +33,7 @@ protected function prefixTable($base_name)
         return $this->table_prefix . $base_name;
     }
 
-    protected function cleanUp()
+    protected function pruneReplacedEvents()
     {
         // No deletions, nothing to do.
         if (empty($this->address_deletion_patterns)) {
@@ -64,7 +64,47 @@ protected function cleanUp()
 
     public function __destruct()
     {
-        $this->cleanUp();
+        $this->pruneReplacedEvents();
+    }
+
+    public function countGarbage()
+    {
+        try {
+            $sth = $this->dbh->prepare('SELECT COUNT(*) garbage FROM ' . $this->prefixTable('lcache_events') . ' WHERE "expiration" < :now');
+            $sth->bindValue(':now', REQUEST_TIME, \PDO::PARAM_INT);
+            $sth->execute();
+        } catch (\PDOException $e) {
+            $this->logSchemaIssueOrRethrow('Failed to count garbage', $e);
+            return null;
+        }
+
+        $count = $sth->fetchObject();
+        return intval($count->garbage);
+    }
+
+    public function collectGarbage($item_limit = null)
+    {
+        $sql = 'DELETE FROM ' . $this->prefixTable('lcache_events') . ' WHERE "expiration" < :now';
+        // This is not supported by standard SQLite.
+        // @codeCoverageIgnoreStart
+        if (!is_null($item_limit)) {
+            $sql .= ' ORDER BY "event_id" LIMIT :item_limit';
+        }
+        // @codeCoverageIgnoreEnd
+        try {
+            $sth = $this->dbh->prepare($sql);
+            $sth->bindValue(':now', REQUEST_TIME, \PDO::PARAM_INT);
+            // This is not supported by standard SQLite.
+            // @codeCoverageIgnoreStart
+            if (!is_null($item_limit)) {
+                $sth->bindValue(':item_limit', $item_limit, \PDO::PARAM_INT);
+            }
+            // @codeCoverageIgnoreEnd
+            $sth->execute();
+        } catch (\PDOException $e) {
+            $this->logSchemaIssueOrRethrow('Failed to collect garbage', $e);
+            return false;
+        }
     }
 
     protected function queueDeletion(Address $address)
diff --git a/src/Integrated.php b/src/Integrated.php
index 4fe9035..d479422 100644
--- a/src/Integrated.php
+++ b/src/Integrated.php
@@ -110,4 +110,9 @@ public function getPool()
     {
         return $this->l1->getPool();
     }
+
+    public function collectGarbage($item_limit = null)
+    {
+        return $this->l2->collectGarbage($item_limit);
+    }
 }
diff --git a/src/L2.php b/src/L2.php
index 8ac53d1..336f946 100644
--- a/src/L2.php
+++ b/src/L2.php
@@ -9,4 +9,6 @@ abstract public function set($pool, Address $address, $value = null, $ttl = null
     abstract public function delete($pool, Address $address);
     abstract public function deleteTag(L1 $l1, $tag);
     abstract public function getAddressesForTag($tag);
+    abstract public function collectGarbage($item_limit = null);
+    abstract public function countGarbage();
 }
diff --git a/src/StaticL2.php b/src/StaticL2.php
index 9902c82..dbf26a3 100644
--- a/src/StaticL2.php
+++ b/src/StaticL2.php
@@ -19,6 +19,31 @@ public function __construct()
         $this->tags = [];
     }
 
+    public function countGarbage()
+    {
+        $garbage = 0;
+        foreach ($this->events as $event_id => $entry) {
+            if ($entry->expiration < REQUEST_TIME) {
+                $garbage++;
+            }
+        }
+        return $garbage;
+    }
+
+    public function collectGarbage($item_limit = null)
+    {
+        $deleted = 0;
+        foreach ($this->events as $event_id => $entry) {
+            if ($entry->expiration < REQUEST_TIME) {
+                unset($this->events[$event_id]);
+                $deleted++;
+            }
+            if ($deleted === $item_limit) {
+                break;
+            }
+        }
+    }
+
     // Returns an LCache\Entry
     public function getEntry(Address $address)
     {
diff --git a/tests/LCacheTest.php b/tests/LCacheTest.php
index 79259bd..16b1de9 100644
--- a/tests/LCacheTest.php
+++ b/tests/LCacheTest.php
@@ -424,6 +424,11 @@ public function testBrokenDatabaseFallback()
 
         // Try applying events to an uninitialized L1.
         $this->assertNull($l2->applyEvents(new StaticL1()));
+
+        // Try garbage collection routines.
+        $pool->collectGarbage();
+        $count = $l2->countGarbage();
+        $this->assertNull($count);
     }
 
     public function testDatabaseL2SyncWithNoWrites()
@@ -638,17 +643,54 @@ public function performFailedUnserializationOnSyncTest($l2)
         $this->assertEquals(1, $l1->getMisses());
     }
 
-    public function testDatabaseL2FailedUnserializationOnSyncTest() {
+    public function testDatabaseL2FailedUnserializationOnSync()
+    {
         $this->createSchema();
         $l2 = new DatabaseL2($this->dbh);
         $this->performFailedUnserializationOnSyncTest($l2);
     }
 
-    public function testStaticL2FailedUnserializationOnSyncTest() {
+    public function testStaticL2FailedUnserializationOnSync()
+    {
         $l2 = new StaticL2();
         $this->performFailedUnserializationOnSyncTest($l2);
     }
 
+    public function performGarbageCollectionTest($l2)
+    {
+        $pool = new Integrated(new StaticL1(), $l2);
+        $myaddr = new Address('mybin', 'mykey');
+        $this->assertEquals(0, $l2->countGarbage());
+        $pool->set($myaddr, 'myvalue', -1);
+        $this->assertEquals(1, $l2->countGarbage());
+        $pool->collectGarbage();
+        $this->assertEquals(0, $l2->countGarbage());
+    }
+
+    public function testDatabaseL2GarbageCollection()
+    {
+        $this->createSchema();
+        $l2 = new DatabaseL2($this->dbh);
+        $this->performGarbageCollectionTest($l2);
+    }
+
+    public function testStaticL2GarbageCollection()
+    {
+        $l2 = new StaticL2();
+        $this->performGarbageCollectionTest($l2);
+
+        // Test item limits.
+        $pool = new Integrated(new StaticL1(), $l2);
+        $myaddr2 = new Address('mybin', 'mykey2');
+        $myaddr3 = new Address('mybin', 'mykey3');
+        $pool->collectGarbage();
+        $pool->set($myaddr2, 'myvalue', -1);
+        $pool->set($myaddr3, 'myvalue', -1);
+        $this->assertEquals(2, $l2->countGarbage());
+        $pool->collectGarbage(1);
+        $this->assertEquals(1, $l2->countGarbage());
+    }
+
     /**
     * @return PHPUnit_Extensions_Database_DataSet_IDataSet
     */
@@ -657,3 +699,4 @@ protected function getDataSet()
         return new \PHPUnit_Extensions_Database_DataSet_DefaultDataSet();
     }
 }
+