Sixty-four adult patients (87 diaphyseal forearm fractures) were treated by plating. Thirty-nine percent of the fractures were classified as single bone fractures (16% radius, 23% ulna); 43% were both radial and ulnar fractures, and 19% were Galeazzi or Monteggia fracture-dislocations. A major complication occurred in 18 (28%) patients. Nonunion occurred in six patients: three of 18 bones treated with four screws (17%), but only three of 69 bones fixed with five or more screws (4.3%), a nonunion rate four times higher for bones plated with four screws. Screws loosened in three fractures, all involving the ulna. Radioulnar synostosis occurred in seven forearms, and in five of these the forearm injuries were associated with multiple system trauma involving head injury. Two patients had osteomyelitis. Both were victims of massive crush injury and delayed internal fixation, and both required removal of the implant; but eventually the fractures healed. Plate fixation of forearm fractures can have a high complication rate. Meticulous attention to surgical technique and the use of plates long enough to provide secure fixation can not be overemphasized. An increased incidence of synostosis in polytrauma, head-injured patients was noteworthy.