1. A patient with macrodactyly of the middle finger of the left hand was followed up from birth until the finger was amputated at the age of three. 2. The affected finger, besides showing gigantism at birth, grew at a faster rate than the normal fingers. The degree of bone maturation (as judged from the appearance and size of the phalangeal ossification centres) proceeded at a faster rate than the normal fingers. No vascular abnormality which could account for the gigantism was detected either radiologically or microscopically. The affected finger showed histological abnormalities of both bone and soft tissues.