In nine patients of median age 34 years who had sustained an amputation of the thumb at a median 24 (5 to 131) months previously, we lengthened the first metacarpal by 30 (17 to 36) mm. Seven amputations had been through the proximal phalanx and two through the metacarpal. The first two patients had autogenous grafting at a second stage, but the other seven had callotasis alone. In these patients the external fixators were removed at a median 189 (115 to 271) days after osteotomy. In six cases the adductor pollicis tendon was transferred proximally and the first web deepened. There was late fracture or palmar flexion of the callus in five patients, but this required further surgery in only one. Treatment was complete at 326 (140 to 489) days after osteotomy. The extended thumb retained its sensitivity; both grasp and key-pinch strength were satisfactory and only one patient felt that the result did not warrant the long course of treatment. Metacarpal lengthening by this method is a prolonged procedure, but provides a valuable alternative to more complex reconstructions