To evaluate the frequency of different types of forearm fractures and, in particular, determine the frequency of double injury to the forearm, the authors prospectively examined 119 consecutive forearm fractures and found double injuries to the forearm in all but five cases. In 79 of the 119 patients (66%), ligamentous injury was seen in addition to the obvious fracture. Nine patients with apparent isolated fractures on initial radiographs underwent examination by means of radionuclide bone scanning, which revealed a second injury in eight of them. Four patients with apparent single fractures did not undergo bone scanning because of their critical conditions. In four patients, a single fracture was initially diagnosed, but after reduction and casting, dislocation of the radioulnar joint was seen. These findings indicate that injury to the forearm almost invariably occurs at two or more sites and involves either both bones or bone and ligament. Because the distal radioulnar joint was affected in 71 patients (60%), scrutiny of the wrist is imperative whenever injuries to the bones of the forearm are discovered.