Many controversies remain in Perthes'. These algorithms are presented as a way through the maze of contradictory and incomplete evidence. Catterall has emphasised the importance of clinical examination in the assessment of cases of Perthes' and this is particularly important in the younger group, many of whose hips heat very round, despite rather adverse-looking X-rays early on, because they have maintained an excellent, almost normal, range of movements. The older child or early adolescent with Perthes' requires urgent attention, as the femoral head lacks the regenerative capacity of the younger child. Before any operation in Perthes', action must be taken to unstiffen the hip. Containment procedures wilt fait if performed on a stiff hip and even salvage procedures are best performed on a hip that has been loosened as much as possible. Surgeons need to recall that most untreated Perthes' do not require intervention until the age of 40. If our interventions on the child result in hip replacement being required in the 20's, then we have not done that patient a service. (C) 2004 Elsevier Ltd. All rights reserved.