A group of children with Legg-Calvé-Perthes disease (LCPD) who underwent femoral osteotomy were analyzed to define further those most likely to respond favorably to this procedure. Treatment was directed to removal of the protruded, flattened, and damaged osteochondral head segment--as delineated by arthrography--from the damaging influence of the lateral acetabular lip and to expose the head to the molding influence of the acetabulum during weight-bearing and motion. This containment of the head was achieved by employing femoral varus-derotation (and sometimes extension) osteotomy. "Reversed" and "open" wedge techniques were also used to minimize limb shortening. Overall results were 83% satisfactory and 17% unsatisfactory according to Mose's criteria. Operation is recommended in the early clinical and radiologic stage of the disease, when favorable biologic and biomechanical effects may be anticipated. In the late stages of LCPD, osteotomy may be used as a salvage procedure in painful and deformed hips, while still maintaining a passive range of motion. An expectant approach can be adopted in children less than 4 years of age, but undue delay in operation, if femoral head protrusion is demonstrated by arthrography, may compromise the final results.