diff -r 398073b195bb src/video/cocoa/SDL_cocoamouse.m
--- a/src/video/cocoa/SDL_cocoamouse.m	Fri Dec 14 23:05:34 2012 -0800
+++ b/src/video/cocoa/SDL_cocoamouse.m	Sat Dec 15 20:18:07 2012 +1030
@@ -179,6 +179,14 @@
     CGWarpMouseCursorPosition(point);
 }
 
+/*
+ * It seems that after calling CGAssociateMouseAndMouseCursorPosition(false),
+ * the first relative event will report the jump from current position back to
+ * whatever fixed point it is going to report from then onwards. Simplest
+ * thing to do seems to be just ignore the first relative event.
+ */
+static SDL_bool ignore_one_relative_event = SDL_FALSE;
+
 static int
 Cocoa_SetRelativeMouseMode(SDL_bool enabled)
 {
@@ -193,6 +201,9 @@
         SDL_SetError("CGAssociateMouseAndMouseCursorPosition() failed");
         return -1;
     }
+
+    ignore_one_relative_event = enabled;
+
     return 0;
 }
 
@@ -216,6 +227,11 @@
 {
     SDL_Mouse *mouse = SDL_GetMouse();
 
+    if (mouse->relative_mode && ignore_one_relative_event) {
+        ignore_one_relative_event = SDL_FALSE;
+        return;
+    }
+
     if (mouse->relative_mode &&
         ([event type] == NSMouseMoved ||
          [event type] == NSLeftMouseDragged ||