A prosthesis which functions as a thumb or other digit in a hand which has only one functioning digit was used on thirteen patients—twelve with traumatic amputation or amputation of most of the hand for tumor and one with congential ectrodactylia. Adjuvant surgery was often needed for maximum function, but the result was always more satisfactory than that after multiple attempts at reconstruction with a new digit. The prosthesis is made of plastic and is leather lined on the prehensile surface. It is strapped to the forearm for use.