Acetabular development in adolescence was assessed in 61 patients with congenital dislocation of the hip (CDH). Limbectomy was performed in 31; in these, the lateral acetabular (iliac) epiphysis failed to appear by age 13 years. This failure was associated with loss of cover of the femoral head in patients followed up until the third decade. The lateral acetabular epiphysis appeared in all remaining patients in whom reduction was achieved without limbectomy. Acetabular development in adolescence is affected adversely by limbectomy; this is due at least in part to absence of the lateral acetabular epiphysis.