A 39-year-old man with generalized tonic clonic epilepsy and profound mental retardation sustained 18 fractures (15 in appendicular and 3 in axial bones) during 19 years. Both femoral necks were fractured, requiring surgical repair. Although he had been on antiepileptic drugs for 35 years, he had no radiographic or biochemical sign of osteomalacia. He had a very low bone mineral density, suggesting osteoporosis. This case illustrates an important medical problem affecting people with developmental disability and a management challenge for their caretakers.