The aim of this study was to assess the rate of hip dislocation at different ages in children with bilateral spastic cerebral palsy attending special schools in southern Derbyshire, UK, between 1985 and 2000. The medical notes of 110 individuals (68 males, 42 females) were obtained. They were divided into four groups according to the Gross Motor Function Classification System (GMFCS). We determined whether or not their hips were dislocated at the ages of 5, 10, and 15 years, and the kind of surgery performed in each case. The percentage of individuals with one or both hips dislocated increased with age and with severity of disease. Of those in GMFCS Level II (n=18), none had dislocations; Level III (n=16), none had dislocations at ages 5 and 10, but 11% had by the age of 15; Level IV (n=35), 8% had dislocations by age 5, 19% by age 10, and 30% by age 15; Level V (n=41), 22% had dislocations by age 5, 48% by age 10, and 50% by age 15. Forty-two per cent of individuals with hip dislocation had not had previous preventive surgery. Twenty-one per cent of hips operated on still proceeded to dislocation. We conclude that there was a high rate of hip dislocation, especially in GMFCS groups Levels IV and V, and that this often occurred very early. Preventive surgery avoided dislocation in many children. However, orthopaedic referral was often not made before dislocation was discovered, or the referral was made too late for surgery on soft tissue to be successful. These results may be compared with those from current programmes of hip management, involving radiological surveillance and early use of conservative and surgical interventions.