We analyzed various prognostic factors in 112 children operated on for Perthes' disease (Catterall's groups II-IV); special attention was paid to acetabular changes and postoperative containment. The radiographic results of 126 intertrochanteric femoral varus osteotomies were analyzed 2-16 years postoperatively. Catterall's grouping or head-at-risk phenomenon, bicompartmentalization of the acetabulum, and preoperative subluxation of the femoral head did not correlate with the result. The result was worse in cases operated on in the healing phase of the disease and in patients operated on at the age of 9 years or older. The strongest prognostic factor was containment of the femoral head after osteotomy.