We conducted a retrospective review of the results of twenty-seven consecutive osteotomies for malunited fractures of the forearm performed at the Mayo Clinic from 1976 to 1991. There were seventeen male patients and ten female patients who were an average of nineteen years old (range, nine to forty-one years old) at the time of the osteotomy. The corrective osteotomy was performed an average of seventy-three months (range, two to 324 months) after the fracture. The indication for the procedure was functional loss of motion (average arc of pronation-supination, 74 degrees; range, 20 to 120 degrees) in twenty patients, an unstable and painful distal radioulnar joint in six, and an unacceptable appearance of the forearm in one. Twenty patients had a corrective osteotomy of the radius; two, of the ulna; and five, of both bones. Of the twenty patients who had a corrective osteotomy for loss of motion of the forearm, nine were managed within twelve months after the initial injury and eleven were managed more than twelve months afterward. The patients who were managed early gained an average of 79 degrees (range, 20 to 160 degrees) of rotation after the osteotomy. Those who were managed late gained an average of only 30 degrees (range, -25 to 95 degrees). A pain-free, stable wrist was achieved in three of the six patients who were managed for an unstable and painful distal radio-ulnar joint. However, these six patients lost an average of 7 degrees (range, -25 to 25 degrees) of rotation of the forearm.(ABSTRACT TRUNCATED AT 250 WORDS)