A minority of cases of osteopetrosis show in addition syndactyly and distal phalangeal anomalies. The seven cases that have been reported with this combination have had an unusual degree of density and thickening of the skull vault, face and mandible, and of the shafts of the metacarpals, metatarsals, proximal phalanges and clavicles. It is submitted that these features constitute a distinct morphological variety of osteopetrosis.