The development of dysplasia of the hip in cerebral palsy has been studied in 292 hips in children. The rate of migration of the hip has been defined, and gave a very early indication of the prognosis for the dysplasia. A close relationship was also found between the early radiographic changes and the functional locomotor anatomy. By reviewing the initial radiographs the need for early treatment and its adaptation to the future locomotor potential of the child can be assessed. Treatment is usually by musculotendinous releases and is especially effective in early recentering of the femoral head, but this method is ineffective in correcting bone dysplasia, particularly acetabular obliquity, which starts at around the age of 30 months. It is preferable to anticipate its development by early tenotomies which are much better tolerated than pelvic osteotomy in spastic children.