Index: intern/ghost/GHOST_Types.h
===================================================================
--- intern/ghost/GHOST_Types.h	(revision 24467)
+++ intern/ghost/GHOST_Types.h	(working copy)
@@ -373,2 +373,4 @@
 	GHOST_TInt32 z;	
+	/** Horizontal scroll wheel. */
+	GHOST_TInt32 w;
 } GHOST_TEventWheelData;
Index: intern/ghost/intern/GHOST_EventWheel.h
===================================================================
--- intern/ghost/intern/GHOST_EventWheel.h	(revision 24467)
+++ intern/ghost/intern/GHOST_EventWheel.h	(working copy)
@@ -51,7 +51,9 @@
 	 * @param type		The type of this event.
-	 * @param z			The displacement of the mouse wheel.
+	 * @param w			The horizontal displacement of the mouse wheel.
+	 * @param z			The vertical displacement of the mouse wheel.
 	 */
-	GHOST_EventWheel(GHOST_TUns64 msec, GHOST_IWindow* window, GHOST_TInt32 z)
+	GHOST_EventWheel(GHOST_TUns64 msec, GHOST_IWindow* window, GHOST_TInt32 w, GHOST_TInt32 z)
 		: GHOST_Event(msec, GHOST_kEventWheel, window)
 	{
+		m_wheelEventData.w = w;
 		m_wheelEventData.z = z;
Index: intern/ghost/intern/GHOST_SystemCarbon.cpp
===================================================================
--- intern/ghost/intern/GHOST_SystemCarbon.cpp	(revision 24467)
+++ intern/ghost/intern/GHOST_SystemCarbon.cpp	(working copy)
@@ -875,3 +875,3 @@
 					delta = delta > 0 ? 1 : -1;
-					pushEvent(new GHOST_EventWheel(getMilliSeconds(), window, delta));
+					pushEvent(new GHOST_EventWheel(getMilliSeconds(), window, 0, delta));
 					err = noErr;
Index: intern/ghost/intern/GHOST_SystemCocoa.mm
===================================================================
--- intern/ghost/intern/GHOST_SystemCocoa.mm	(revision 24467)
+++ intern/ghost/intern/GHOST_SystemCocoa.mm	(working copy)
@@ -1205,7 +1205,14 @@
 				
-				double deltaF = [event deltaY];
-				if (deltaF == 0.0) break; //discard trackpad delta=0 events
+				double deltaX = [event deltaX];
+				double deltaY = [event deltaY];
 				
-				delta = deltaF > 0.0 ? 1 : -1;
-				pushEvent(new GHOST_EventWheel([event timestamp], window, delta));
+				if (deltaX != 0.0) {
+					delta = deltaX > 0.0 ? 1 : -1;
+					pushEvent(new GHOST_EventWheel([event timestamp], window, delta, 0));
+				}
+				
+				if (deltaY != 0.0) {
+					delta = deltaY > 0.0 ? 1 : -1;
+					pushEvent(new GHOST_EventWheel([event timestamp], window, 0, delta));
+				}
 			}
Index: intern/ghost/intern/GHOST_SystemWin32.cpp
===================================================================
--- intern/ghost/intern/GHOST_SystemWin32.cpp	(revision 24467)
+++ intern/ghost/intern/GHOST_SystemWin32.cpp	(working copy)
@@ -58,2 +58,5 @@
 #endif // WM_MOUSEWHEEL
+#ifndef WM_MOUSEHWHEEL
+#define WM_MOUSEHWHEEL 0x020E
+#endif // WM_MOUSEHWHEEL
 #ifndef WHEEL_DELTA
@@ -509,3 +512,3 @@
 
-GHOST_EventWheel* GHOST_SystemWin32::processWheelEvent(GHOST_IWindow *window, WPARAM wParam, LPARAM lParam)
+GHOST_EventWheel* GHOST_SystemWin32::processWheelEvent(GHOST_IWindow *window, WPARAM wParam, LPARAM lParam, UINT type)
 {
@@ -520,3 +523,7 @@
 	// short yPos = (short) HIWORD(lParam);	// vertical position of pointer
-	return new GHOST_EventWheel (getSystem()->getMilliSeconds(), window, zDelta);
+	if (type == WM_MOUSEHWHEEL) {
+		return new GHOST_EventWheel (getSystem()->getMilliSeconds(), window, zDelta, 0);
+	} else {
+		return new GHOST_EventWheel (getSystem()->getMilliSeconds(), window, 0, zDelta);
+	}
 }
@@ -722,2 +729,3 @@
 				case WM_MOUSEWHEEL:
+				case WM_MOUSEHWHEEL:
 					/* The WM_MOUSEWHEEL message is sent to the focus window 
@@ -729,3 +737,3 @@
 					 */
-					event = processWheelEvent(window, wParam, lParam);
+					event = processWheelEvent(window, wParam, lParam, msg);
 					break;
Index: intern/ghost/intern/GHOST_SystemWin32.h
===================================================================
--- intern/ghost/intern/GHOST_SystemWin32.h	(revision 24467)
+++ intern/ghost/intern/GHOST_SystemWin32.h	(working copy)
@@ -238,3 +238,3 @@
 	 */
-	static GHOST_EventWheel* processWheelEvent(GHOST_IWindow *window, WPARAM wParam, LPARAM lParam);
+	static GHOST_EventWheel* processWheelEvent(GHOST_IWindow *window, WPARAM wParam, LPARAM lParam, UINT type);
 
Index: intern/ghost/intern/GHOST_SystemX11.cpp
===================================================================
--- intern/ghost/intern/GHOST_SystemX11.cpp	(revision 24467)
+++ intern/ghost/intern/GHOST_SystemX11.cpp	(working copy)
@@ -468,3 +468,3 @@
 			if (xe->xbutton.button == 4) {
-				g_event = new GHOST_EventWheel(getMilliSeconds(), window, 1);
+				g_event = new GHOST_EventWheel(getMilliSeconds(), window, 0, 1);
 				break;
@@ -472,5 +472,14 @@
 			if (xe->xbutton.button == 5) {
-				g_event = new GHOST_EventWheel(getMilliSeconds(), window, -1);
+				g_event = new GHOST_EventWheel(getMilliSeconds(), window, 0, -1);
 				break;
 			}
+			if (xe->xbutton.button == 4) {
+				g_event = new GHOST_EventWheel(getMilliSeconds(), window, 1, 0);
+				break;
+			}
+			if (xe->xbutton.button == 5) {
+				g_event = new GHOST_EventWheel(getMilliSeconds(), window, -1, 0);
+				break;
+			}
+			
 		}
Index: source/blender/windowmanager/intern/wm_event_system.c
===================================================================
--- source/blender/windowmanager/intern/wm_event_system.c	(revision 24467)
+++ source/blender/windowmanager/intern/wm_event_system.c	(working copy)
@@ -1717,4 +1717,8 @@
 				event.type= WHEELUPMOUSE;
-			else
+			else if (wheelData->z < 0)
 				event.type= WHEELDOWNMOUSE;
+			else if (wheelData->w < 0)
+				event.type= WHEELLEFTMOUSE;
+			else if (wheelData->w > 0)
+				event.type= WHEELRIGHTMOUSE;
 			
Index: source/blender/windowmanager/wm_event_types.h
===================================================================
--- source/blender/windowmanager/wm_event_types.h	(revision 24467)
+++ source/blender/windowmanager/wm_event_types.h	(working copy)
@@ -64,2 +64,4 @@
 #define WHEELDOWNMOUSE	0x00b
+#define WHEELLEFTMOUSE	0x00e	
+#define WHEELRIGHTMOUSE	0x00f
 		/* mapped with userdef */