Perthes' disease may be regarded as a generalised disorder of cartilage development in which there is a particular predisposition for repeated episodes of infarction in the proximal femoral epiphysis. The resulting deformation of the head is due to collapse of the ossific nucleus and irregular growth of the cartilage. The shape of the epiphysis is determined by the pressure of the surrounding structures. The most ominous factors determining prognosis are onset in the older child, epiphysial protrusion, extensive involvement of the epiphysis and arrest of subcapital growth. The overall prognosis is determined by the quality of preservation of the sphericity of the head, with maldevelopment leading to osteoarthritis. The aim of treatment is to achieve sphericity by containing the epiphysis within the acetabulum. A uniform regime of management cannot be recommended for all patients. Prolonged weight relief in containment appears to be the most satisfactory method of treatment in those with a pour prognosis. Operation is necessary to provide containment in the presence of ephiphyseal protrusion, and may also shorten the length of treatment in some younger patients. In the majority of young children the use of abduction braces which permit walking is recommended. In children with a minor degree of involvement a short period of bedrest may be all that is required. Overtreatment of young children should be avoided, as should undertreatment in the older age groups.