One year after rupture of the 5th flexor profundus tendon, a 45-year-old man showed signs of carpal tunnel syndrome. At surgery the proximal stump of the 5th flexor profundus tendon was found in the carpal tunnel. Due to an anomalous origin of the 4th lumbrical muscle from the profundus tendon of the 4th finger the proximal stump of the 5th flexor profundus tendon had withdrawn far proximally and in this way produced a carpal tunnel syndrome.