Although hypercalcemia has long been recognized as a complication of sarcoidosis, the incidence of hypercalcemia (> or = 11 mg/dl) in Japan is probably less than 5%. 1 alpha, 25(OH)2D3 is the main cause for hypercalcemia in sarcoidosis and overproduced by sarcoid granulomata. Gamma-interferon produced by activated lymphocytes and macrophages plays a major role in the synthesis of 1 alpha, 25(OH)2D3. PTH release is down regulated by high serum concentration of 1 alpha, 25(OH)2D3. Parathyroid hormone related protein may also contribute to the hypercalcemia of sarcoidosis. Treatment of hypercalcemia and hypercalciuria consists of a low calcium diet, adequate hydration, minimization of exposure to sunlight and reducing overproduction of 1 alpha, 25(OH)2D3. Prednisone, 15 to 25 mg/day, is the drug of choice to reduce the overproduction of 1 alpha, 25(OH)2D3.