ONE of the complications of mental retardation and spastic cerebral palsy in children is bone demineralization accompanied by pathologic fractures. The demineralization is apparently due to nonambulation and/or poor nutrition, both of which are difficult to correct in these patients. Previous studies in adults have shown a variety of effects on bone and on calcium and phosphorus metabolism during treatment of demineralizing conditions with sodium fluoride,1-8 sex hormone and anabolic steroids,9-20 and inorganic phosphates.21-23 During the treatment of permanently bedfast children in an institution for the mentally retarded, a study was made to compare the effects of sodium fluoride, oxymetholone (an anabolic steroid), and inorganic phosphates on bone density. All of the patients had low bone densities for age as compared to 200 ambulatory patients in the same institution; 68 had bone demineralization which could be determined by visual inspection of x-ray films of the humerus or