Of 155 institutionalized epileptics, 16 (10%) were noted to have suffered from different kinds of fractures when observed over a period of 1 year. The patients with fractures were further investigated with respect to blood and urine chemistry and bone morphology. The serum and urinary calcium values were below the average values for the population. Elevated values for serum alkaline phosphatase and for immunoreactive parathyroid hormone were found in most patients. The values of serum phosphate were distributed close to those of the normal population, while the urinary phosphate values were lower. Examination of bone biopsies revealed a significantly increased amount of osteoid and a significantly increased osteoclastic resorptive activity in epileptics, compared with age-matched controls. Furthermore, a slightly diminished volume of trabecular bone was noted. The high incidence of fractures may be explained by bone disease--a combination of osteoporosis, osteomalacia, and hyperparathyroidism due to chronic treatment with anticonvulsant drugs.