A subtrochanteric osteotomy was performed on 25 hips of 24 patients affected with Perthes disease. Twelve of these patients have been followed 4 or more years postoperatively. Coxa plana, or "mushroom" deformity, never occurred. Roundness of the head was always achieved. Internal fixation was first secured with a 4 screw plate and later advantageously substituted by Hoffmann external fixation. Post-operative shortening was always present but gradually resolved to less than 1 cm in most cases. A Trendelenburg positive sign was always present postoperatively and usually disappeared within 2 years. Internal rotation of 40-60 degrees was obtained at surgery. The resulting external rotation deformity of the leg corrected spontaneously. Varus deformity, on the other hand, changed little within this follow-up. Varisation of the hip is nevertheless an essential part of the osteotomy. The overall results were directly related to the amount of epiphysis involved. The fate of the epiphyseal plate seems to play a major role in the neck deformities and the resulting coxa vara. The absence of metaphyseal changes in the face of significant epiphyseal involvement is an ominous sign.