The bone mineral content of the radius has been determined by the method of Cameron and Sorenson in normal subjects and in patients with osteoporosis, osteomalacia, hyperparathyroidism, hypoparathyroidism, osteogenesis imper fecta and recurrent renal calculi. The bone mineral content of the radius is a clinically reproducible measurement and useful for the diagnosis and quantification of changes in bone mineral. The mineral content of the radius was diminished in two patients with hyperparathyroidism where routine radiographs and serum alkaline phosphatase activity were normal. This measurement was normal in patients with idiopathic hypercalciuria and recurrent renal calculi and in the majority of patients with hypoparathyroidism.