Congenital absence of the median-innervated intrinsic muscles and flexor pollicis longus was seen in varying degrees of severity in eleven hands of eight patients. Three members were involved in one family in which the anomaly was probably an autosomal dominant. There were no chromosomal abnormalities. Surgical treatment of seven hands, including release of the adduction contracture and transfer of the ring-finger superficialis tendon to provide opposition and to reinforce the ulnar collateral ligament of the metacarpophalangeal joint, resulted in significant improvement in pinch and grasp.