The clinical, pathologic, and roentgenographic features of macrodactylia fibrolipomatosis described are based on 40 cases from the literature and five cases seen by the authors. This condition previously has been described as macrodactyly, megalodactyly, macrodystrophia lipomatosa, dactylomegaly, and local gigantism. We believe macrodactylia fibrolipomatosis is the best term because it describes the characteristics which separate this condition from other forms of macrodactyly. Macrodactylia fibrolipomatosis is a form of macrodactyly noticed soon after birth. Usually affected are multiple adjacent digits on the lateral aspect of the hand or the medial aspect of the foot, although a single digit may be involved. Roentgenograms show bony enlargement, often with medial deviation in the hand and lateral deviation in the foot. The soft tissues ventral to the affected bones are diffusely enlarged and are predominantly of fat density, commonly mixed with bands of denser connective tissue. The cause of this rare condition is obscure but it may be related to fibrofatty tumors, often found at surgery, impinging on nerves supplying the enlarged digits.