diff --git a/README.txt b/README.txt
index ff5015d..1b81b28 100644
--- a/README.txt
+++ b/README.txt
@@ -83,6 +83,19 @@ Configuration Variables
     ),
   );
 
+  Querying a slave is also possible by creating a new connection alias
+  and specifying slave_ok option.
+
+  $conf['mongodb_connections'] = array(
+    // Connection name/alias
+    'slave' => array(
+      'host' => 'slave1',
+      // Database name
+      'db' => 'drupal_default',
+      'slave_ok' => TRUE,
+    ),
+  );
+
 #2: mongodb_debug
 
   A variable primarily for developers, mongodb_debug causes a collection
diff --git a/mongodb.module b/mongodb.module
index c5e4afa..69cf3b1 100644
--- a/mongodb.module
+++ b/mongodb.module
@@ -32,6 +32,9 @@ function mongodb($alias = 'default') {
   if (!isset($mongo_objects[$host][$db])) {
     try {
       $mongo = new Mongo($host, $options);
+      if (!empty($connection['slave_ok'])) {
+        $mongo->setSlaveOkay(TRUE);
+      }
       $mongo_objects[$host][$db] = $mongo->selectDB($db);
       $mongo_objects[$host][$db]->connection = $mongo;
     }