1. Of 1013 hospitalized patients with cerebral palsy, 274 patients with dislocated or subluxated hips have been studied, a prevalence of 28 per cent. This figure is high because severely involved, neurologically and developmentally immature quadriplegic patients constituted a large fraction of the hospital population.
2. The mean age at which dislocation occurred in 139 of these patients was seven years.
3. It is proposed that retained neonatal reflexes, muscle imbalance and contracture, coxa valga, femoral anteversion, and acetabular index are responsible for the dislocations.
4. The results and complications of the 518 combined operations are summarized.
5. Correction of coxa valga and of femoral anteversion are the most important surgical considerations in the prevention and treatment of dislocation of the hip in cerebral palsy.