Diaphyseal malunion of the forearm may cause loss of pronation and supination, a painful distal radioulnar joint, and aesthetic problems. Seventeen patients (10 males, seven females; mean age, 20.6 +/- 9.3 years) were operated on because of symptomatic malunion after a pediatric forearm fracture. Six patients had predominant loss of pronation (Group 1), four had predominant loss of supination (Group 2), and seven had a painful distal radioulnar joint (Group 3). An osteotomy of the radius was performed in seven patients and of both forearm bones in 10. All patients were available for clinical and radiologic assessments at a minimum followup of 6 months (mean +/- standard deviation, 3.7 +/- 2.3 years; range, 0.5-9.9 years). Release of the contracted interosseous membrane frequently was necessary for patients in Groups 1 and 2 to allow for correction and did not result in weakness, instability of the distal radioulnar joint, or synostosis. The overall improvement in range of motion after osteotomies for patients with a supination deficit was much better than in those with a pronation deficit. All patients in Group 3 gained a pain-free and stable distal radioulnar joint and their range of motion was unchanged. Therefore, ability to improve overall range of motion through forearm osteotomies is dependent on the patients' preoperative complaint. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.