In hands in which the superficial flexors of the fingers and thenar muscles of opposition are denervated, usually as the result of high median-nerve or brachial plexus injury, thumb opposition can be restored by transfer of the superficial flexor of the ring finger to the thumb through a dynamic pulley made from the distal segment of flexor carpi ulnaris which is attached to the proximal segment of flexor carpi ulnaris to the transferred paralyzed superficial ring-finger flexor tendon. Of sixteen patients treated by this method, twelve had good or satisfactory results; one had a poor result; and three were lost to follow-up.