Legg-Calvé-Perthes disease remains indefinite from an etiologic point of view and unforeseable in its evolution. The evolution depends on the extent of epiphyseal involvement and the age of the child. It may safely be stated that the more extensive the epiphyseal involvement, the more compromised is the prognosis. Also the older the child, the more the femoral head remoulding will be limited. Preserving articular mobility and containing the head within the depth of acetabulum constitute the mainstay of treatment aiming for a femoral head as spherical as possible upon completion of growth. At the end of growth spherical or ovoid heads will cause no or few problems, however strongly deformed femoral heads will evolve into early hip arthritis. The early recognition of which hip will profit from which treatment, constitutes the major difficulty of the therapeutic process.