This study was to determine the outcome of 5 years of vitamin D supplementation in children and adults with spastic quadriplegia living in a long-term care facility where a high incidence of pathological fractures had been noted. Twenty of 88 patients with spastic quadriplegia had sustained 56 atraumatic fractures in the 4 years before this study. The median age was 17.5 years (6 to 29). An earlier study showed that rickets and osteomalacia were more severe in the patients with fractures. There was a significant relationship (p =0.002) between the number of fractures and the use of anticonvulsant therapy (ACT). The fractures were treated conservatively. ACT was continued. The patients were initially given 5000 IU of calciferol a day for 3 months, followed by a maintenance dose of 50 000 IU (one capsule) a month. Vitamin D supplementation was extended to all non-ambulatory patients, who spent most of their time indoors and had little exposure to sunlight. Two of the 20 patients with fractures died of respiratory complications in the first year of the study and one was discharged. At 5-year follow-up, when 17 were assessed, none had pain on movement of the previously fractured limbs. In 14 patients, the fractures had healed in acceptable alignment. Three patients who had sustained multiple fractures had severe bowing deformities of the affected limbs. Since the implementation of the intervention, no non-ambulatory patient in the facility has sustained a fracture. We recommend vitamin D supplementation for children and adults with cerebral palsy if exposure to sunlight cannot be guaranteed.