Multiple hereditary exostosis (MHE) can cause progressive skeletal deformities (eg, ulnar shortening, bowing, radial head dislocation) in the upper extremity. Various procedures have been used to correct forearm deformity in children with MHE. The timing of these procedures, however, is controversial. An 11-year-old boy with known MHE presented 7 months after onset of left elbow pain and loss of flexion-extension to 40° to 120°. Radiographs showed a distal ulna osteochondroma, ulnar shortening, bowing, and radial head dislocation. Eighteen months after ulnar osteotomy, radial head reduction, and external fixation, he had motion from 0° to 135°. This case demonstrates that later stage MHE-induced forearm deformities can be successfully surgically corrected. Given possible recurrence during growth, there may be an indication for waiting until the patient is closer to skeletal maturity before proceeding with corrective forearm procedures.