The majority of cases of Madelung deformity are caused by hereditary dyschondrosteosis at the wrist. The principal lesion in the ulnar zone of the distal radial physis retards growth asymmetrically, especially in late childhood. Resection of this zone and its replacement with autologous fat (Langenskiöld procedure, or physiolysis) restores growth and minimizes deformity. The resection of an abnormal ligament tethering the lunate proximally may assist carpal advancement. A series of 17 patients (24 wrists) treated over a 12-year period is presented, with sufficient follow-up for evaluation of 11 patients (15 wrists). The results of this prophylactic procedure are encouraging, and, if it is performed early, the authors believe that Madelung deformity may be preventable, or at least controllable.