In clinical practice fractures of the forearm bones are encoutered as frequently as fractures of other bones. As has been pointed out in many articles, however, the surgical anatomy of the forearm evokes problems in dealing with the diaphyseal fractures of the forearm bones not found in the treatment of diaphyseal fractures of other long bones, The authors have experienced 107 cases of diaphyseal fractures of the forearm bones during the fiveyear period from January, 1972 through December, 1976. A comparison has been made between the two groups one treated by conservative method and the other by open reduction and internal fixation. The results are as follows: 1. The time required for the healing of the fractures was shorter in the conservatively treated group. 2. Restoration of function was more satisfactory in the surgically treated group. 3. Rotational and angulatory deformities were less in the surgically treated group. 4. Forty-one fractures were internally fixed with compression plates, the union rate of which was 100%.