diff --git activity.module activity.module
index 73d3d8c..00b938a 100644
--- activity.module
+++ activity.module
@@ -124,6 +124,27 @@ function user_activity_info() {
   return $info;
 }
 
+function flag_activity_info() {
+  $info = _activity_activity_info();
+  $info->name = 'flag';
+  $info->object_type = 'flag';
+  // The order of objects here matters. If a user is both the author and the
+  // flagging user, the flagging user message takes precedence.
+  $info->objects = array('node author' => 'node', 'flagging user' => 'account', 'comment author' => 'comment');
+  $info->hooks = array('flag' => array('flag', 'unflag'));
+
+  // Figure out the activity access control realms and the types.
+  $flags = flag_get_flags();
+  foreach ($flags as $fid => $flag) {
+    $info->realms["flag_" . $flag->fid] = $flag->title;
+    // Currently, flagging a user cannot be recorded.
+    if ($flag->content_type != 'user') {
+      $info->type_options[$flag->fid] = $flag->title;
+    }
+  }
+  return $info;
+}
+
 /**
  * Implementation of hook_help().
  */
diff --git modules/flag.activity.inc modules/flag.activity.inc
new file mode 100644
index 0000000..c336067
--- /dev/null
+++ modules/flag.activity.inc
@@ -0,0 +1,65 @@
+<?php
+// $Id$
+
+/**
+ * @file
+ * Activity definition file for flag.module
+ */
+
+/**
+ * Implementation of hook_activity_grants().
+ */
+function flag_activity_grants($activity) {
+  $flags = flag_get_flags();
+  $realms = array();
+  // Assign all those flags for nodes.
+  foreach ($flags as $fid => $flag) {
+    // This will also work for comments as those activity records have nids.
+    if ($activity->nid && $flag->content_type == 'node') {
+      $realms['flag_' . $flag->fid] = array($activity->nid);
+    }
+    elseif ($flag->content_type == 'user') {
+      $realms['flag_' . $flag->fid] = array($activity->uid);
+    }
+  }
+  return $realms;
+}
+
+/**
+ * Implementation of hook_activity_access_grants().
+ */
+function flag_activity_access_grants($account) {
+  // Get all the user and node flags.
+  $user_flags = flag_get_user_flags('user', NULL, $account->uid);
+  $node_flags = flag_get_user_flags('node', NULL, $account->uid);
+
+  $flag_grants = array();
+  if (!empty($node_flags)) {
+    foreach ($node_flags as $flagged_objects) {
+      foreach ($flagged_objects as $nid => $flagged) {
+        // Tell activity to grant user $account access to those flagged with
+        // $fid that are $nid.
+        $flag_grants['flag_' . $flagged->fid][] = $nid;
+      }
+    }
+  }
+
+  if (!empty($user_flags)) {
+    foreach ($user_flags as $flagged_objects) {
+      foreach ($flagged_objects as $uid => $flagged) {
+        // Tell Activity to grant user $account access to those flagged with
+        // $fid that are $uid.
+        $flag_grants['flag_' . $flagged->fid][] = $uid;
+      }
+    }
+  }
+
+  return $flag_grants;
+}
+
+/**
+ * Implementation of hook_activity_type_check().
+ */
+function flag_activity_type_check($token_objects, $types) {
+  return (in_array($token_objects['flag']->fid, $types));
+}