A case is reported of a twenty-one year old man who developed severe hypercalcemia late in the diuretic phase of acute reversible renal failure secondary to severe trauma. Hypercalcemia persisted for approximately five months. Serum immunoreactive parathyroid hormone levels were undetectable and sub-total parathyroidectomy had no appreciable effect on the serum calcium. The most likely source of this patient's hypercalcemia was resorption of calcium from metastatic deposits in soft tissue and possibly from bone. Failure to incorporate calcium into bone during the period of immobilization may explain the prolonged hypercalcemia.