diff --git a/accessible/src/base/nsAccessibilityAtomList.h b/accessible/src/base/nsAccessibilityAtomList.h
index e565c278826d..3f548ae5ae0c 100755
--- a/accessible/src/base/nsAccessibilityAtomList.h
+++ b/accessible/src/base/nsAccessibilityAtomList.h
@@ -170,6 +170,7 @@ ACCESSIBILITY_ATOM(href, "href") // XUL, XLink
 ACCESSIBILITY_ATOM(increment, "increment") // XUL
 ACCESSIBILITY_ATOM(lang, "lang")
 ACCESSIBILITY_ATOM(linkedPanel, "linkedpanel") // XUL
+ACCESSIBILITY_ATOM(longDesc, "longdesc")
 ACCESSIBILITY_ATOM(maxpos, "maxpos") // XUL
 ACCESSIBILITY_ATOM(minpos, "minpos") // XUL
 ACCESSIBILITY_ATOM(multiline, "multiline") // XUL
diff --git a/accessible/src/html/nsHTMLImageAccessible.cpp b/accessible/src/html/nsHTMLImageAccessible.cpp
index 4abf0387a454..e980f79e0bfe 100644
--- a/accessible/src/html/nsHTMLImageAccessible.cpp
+++ b/accessible/src/html/nsHTMLImageAccessible.cpp
@@ -210,9 +210,46 @@ void nsHTMLImageAccessible::CacheChildren()
   mAccChildCount = childCount;
 }
 
-NS_IMETHODIMP nsHTMLImageAccessible::DoAction(PRUint8 index)
+NS_IMETHODIMP
+nsHTMLImageAccessible::GetNumActions(PRUint8 *aNumActions)
 {
-  if (index == eAction_ShowLongDescription) {
+  NS_ENSURE_ARG_POINTER(aNumActions);
+  *aNumActions = 0;
+
+  if (IsDefunct())
+    return NS_ERROR_FAILURE;
+
+  nsresult rv= nsLinkableAccessible::GetNumActions(aNumActions);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (HasLongDesc())
+    (*aNumActions)++;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsHTMLImageAccessible::GetActionName(PRUint8 aIndex, nsAString& aName)
+{
+  aName.Truncate();
+
+  if (IsDefunct())
+    return NS_ERROR_FAILURE;
+
+  if (IsValidLongDescIndex(aIndex)) {
+    aName.AssignLiteral("showlongdesc"); 
+    return NS_OK;
+  }
+  return nsLinkableAccessible::GetActionName(aIndex, aName);
+}
+
+NS_IMETHODIMP
+nsHTMLImageAccessible::DoAction(PRUint8 aIndex)
+{
+  if (IsDefunct())
+    return NS_ERROR_FAILURE;
+
+  if (IsValidLongDescIndex(aIndex)) {
     //get the long description uri and open in a new window
     nsCOMPtr<nsIDOMHTMLImageElement> element(do_QueryInterface(mDOMNode));
     NS_ENSURE_TRUE(element, NS_ERROR_FAILURE);
@@ -230,7 +267,7 @@ NS_IMETHODIMP nsHTMLImageAccessible::DoAction(PRUint8 index)
     return win->Open(longDesc, NS_LITERAL_STRING(""), NS_LITERAL_STRING(""),
                      getter_AddRefs(tmp));
   }
-  return nsLinkableAccessible::DoAction(index);
+  return nsLinkableAccessible::DoAction(aIndex);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -405,3 +442,29 @@ nsHTMLImageAccessible::GetAreaAccessible(nsIDOMHTMLCollection *aAreaCollection,
 
   return accessible;
 }
+
+////////////////////////////////////////////////////////////////////////////////
+// Private methods
+
+PRBool
+nsHTMLImageAccessible::HasLongDesc()
+{
+  if (IsDefunct())
+    return PR_FALSE;
+
+  nsCOMPtr<nsIContent> content(do_QueryInterface(mDOMNode));
+  return (content->HasAttr(kNameSpaceID_None, nsAccessibilityAtoms::longDesc));
+}
+
+PRBool
+nsHTMLImageAccessible::IsValidLongDescIndex(PRUint8 aIndex)
+{
+  if (!HasLongDesc())
+    return PR_FALSE;
+
+  PRUint8 numActions = 0;
+  nsresult rv = nsLinkableAccessible::GetNumActions(&numActions);  
+  NS_ENSURE_SUCCESS(rv, PR_FALSE);
+
+  return (aIndex == numActions);
+}
diff --git a/accessible/src/html/nsHTMLImageAccessible.h b/accessible/src/html/nsHTMLImageAccessible.h
index 2fe1e2acd845..49123d020c5f 100644
--- a/accessible/src/html/nsHTMLImageAccessible.h
+++ b/accessible/src/html/nsHTMLImageAccessible.h
@@ -55,15 +55,14 @@ class nsHTMLImageAccessible : public nsLinkableAccessible,
   NS_DECL_ISUPPORTS_INHERITED
 
 public:
-  //action0 may exist depends on whether an onclick is associated with it
-  enum { eAction_ShowLongDescription = 1 };
-
   nsHTMLImageAccessible(nsIDOMNode* aDomNode, nsIWeakReference* aShell);
 
   // nsIAccessible
   NS_IMETHOD GetName(nsAString& _retval); 
   NS_IMETHOD GetState(PRUint32 *aState, PRUint32 *aExtraState);
   NS_IMETHOD GetRole(PRUint32 *_retval);
+  NS_IMETHOD GetNumActions(PRUint8 *aNumActions);
+  NS_IMETHOD GetActionName(PRUint8 aIndex, nsAString& aName);
   NS_IMETHOD DoAction(PRUint8 index);
 
   // nsIAccessibleHyperLink
@@ -95,6 +94,25 @@ protected:
   // share area elements but we need to have separate area accessibles for
   // each image accessible.
   nsAccessNodeHashtable *mAccessNodeCache;
+
+private:
+  /**
+   * Determine if this image accessible has a longdesc attribute.
+   *
+   * @returns  true if the longdesc attribute is present.
+   */
+  PRBool HasLongDesc();
+  
+  /**
+   * Used by GetActionName and DoAction to ensure the index for opening the
+   * longdesc URL is valid.
+   * It is always assumed that the highest possible index opens the longdesc.
+   *
+   * @param aIndex  The 0-based index to be tested.
+   *
+   * @returns  true if index is valid for longdesc action.
+   */
+  PRBool IsValidLongDescIndex(PRUint8 aIndex);
 };
 
 #endif
diff --git a/accessible/tests/mochitest/Makefile.in b/accessible/tests/mochitest/Makefile.in
index 941f987b436d..716e74f688f2 100644
--- a/accessible/tests/mochitest/Makefile.in
+++ b/accessible/tests/mochitest/Makefile.in
@@ -47,6 +47,7 @@ include $(topsrcdir)/config/rules.mk
 
 _TEST_FILES =\
 		moz.png \
+		longdesc_src.html \
 		nsIAccessible_actions.js \
 		nsIAccessible_name.css \
 		nsIAccessible_name.xbl \
diff --git a/accessible/tests/mochitest/longdesc_src.html b/accessible/tests/mochitest/longdesc_src.html
new file mode 100644
index 000000000000..37248795dd77
--- /dev/null
+++ b/accessible/tests/mochitest/longdesc_src.html
@@ -0,0 +1,8 @@
+<html>
+<head>
+<title>Mozilla logo</title>
+</head>
+<body>
+<p>This file would contain a longer description of the Mozilla logo, if I knew what it looked like.</p>
+</body>
+</html>
diff --git a/accessible/tests/mochitest/test_nsIAccessibleImage.html b/accessible/tests/mochitest/test_nsIAccessibleImage.html
index e8e09bf1260c..911016a8aca1 100644
--- a/accessible/tests/mochitest/test_nsIAccessibleImage.html
+++ b/accessible/tests/mochitest/test_nsIAccessibleImage.html
@@ -85,7 +85,8 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=429659
       is(height.value, aHeight, "wrong height for " + aID + "!");
     }
 
-    function testThis(aID, aName, aSRC, aWidth, aHeight)
+    function testThis(aID, aName, aSRC, aWidth, aHeight,
+                      aNumActions, aActionNames)
     {
       var elem = document.getElementById(aID);
       var acc;
@@ -110,6 +111,16 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=429659
       ok(attributes, "no attributes on " + aID + "!");
       is(attributes.getStringProperty("src"), aSRC,
          "no correct src attribute for " + aID + "!");
+
+      if (aNumActions) {
+        is(acc.numActions, aNumActions,
+           "Wrong number of actions for " + aID + "!");
+
+        for (index = 0; index < aActionNames.length; index++) {
+          is(acc.getActionName(index), aActionNames[index],
+             "Wrong action name for " + aID + ", index " + index +"!");
+        }
+      }
     }
 
     function doTest()
@@ -147,6 +158,23 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=429659
       // Test linked image with empty alt attribute and title
       testThis("linkedImageEmptyAltAndTitle", "Link to Mozilla Foundation", "moz.png", 93, 42);
 
+      // Image with long desc
+      var actionNamesArray = new Array("showlongdesc");
+      testThis("longdesc", "Image of Mozilla logo", "moz.png", 89, 38, 1,
+               actionNamesArray);
+
+      // Image with click and long desc
+      actionNamesArray = null;
+      actionNamesArray = new Array("click", "showlongdesc");
+      testThis("clickAndLongdesc", "Another image of Mozilla logo", "moz.png",
+               89, 38, 2, actionNamesArray);
+      
+      // Image with click
+      actionNamesArray = null;
+      actionNamesArray = new Array("click");
+      testThis("click", "A third image of Mozilla logo", "moz.png",
+               89, 38, 1, actionNamesArray);
+      
       SimpleTest.finish();
     }
 
@@ -182,5 +210,14 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=429659
   <br>Linked image with empty alt and title:<br>
   <a href="http://www.mozilla.org"><img id="linkedImageEmptyAltAndTitle" src="moz.png" alt=""
      title="Link to Mozilla Foundation"/></a>
+  <br>Image with longdesc:<br>
+  <img id="longdesc" src="moz.png" longdesc="longdesc_src.html"
+       alt="Image of Mozilla logo"/>
+  <br>Image with click and longdesc:<br>
+  <img id="clickAndLongdesc" src="moz.png" longdesc="longdesc_src.html"
+       alt="Another image of Mozilla logo" onclick="alert('Clicked!');"/>
+  <br>Image with click:<br>
+  <img id="click" src="moz.png"
+       alt="A third image of Mozilla logo" onclick="alert('Clicked, too!');"/>
 </body>
 </html>