We report the case of a patient who had weakness of the fourth dorsal interosseous (DI) and third palmar interosseous (PI) muscles resulting in the abducted position of the little finger at rest. Electromyographic abnormalities were limited to only these muscles with partial denervation findings. The results of routine nerve conduction studies and imaging techniques were normal. Clinical and electrophysiological findings suggested that the lesion had occurred distal to the point where the very small motor branches to these muscles exit the deep palmar branch of the ulnar nerve. (C) 1997 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.