Multiple exostosis and Dyschondroplasia (Ollier's disease) are two Osteochondrodysplasia with abnormal cartilagenous growth which hinder growth of the long bones especially. Among other locations, these diseases do not affect the forearms symetrically. The ulnar bone is more often and more severely affected which results in a progressive dislocation of the forearm. The radial shaft bands while the hand incurves medially. The radial head can even dislocate completely. All the deformities of the forearm create a severe handicap. The authors report their surgical experience. Preventive management is the ideal solution and should be carried out before the onset of a complete dislocation (especially before the dislocation of the radial head). Correction should also take growth into consideration. Logically, the shortest bone (the ulnar) should be lengthened and straightened. Since it is not feasible to reasonably correct all deformities entirely by the ulnar lengthening, it is necessary to not only straighten but also to shorten the radial bone. Only regular surveillance of the growth abnormalities throughout childhood can allow a precise evaluation of the required correction necessary at the time of surgery which should be a definite one stage procedure.