Eighty-seven children less than 16 years of age with recent spinal cord injury were studied during a 7-year period (1970--1976). Serum calcium concentration was determined at least once in each of 76 of these patients, and in 18 (23.6%) it was above 11 mg%. Fifteen of the 18 patients had quadriplegia and 3 had paraplegia. In 5 patients, the first symptoms of acute hypercalcemia simulated those of an acute abdomen. Two of the 5 patients underwent exploratory laparotomy, with negative findings. The incidence of urinary stones was 55% (10 of the 18), a difference from the control population of only 18%. Hypercalcemia in the acute phase was almost always accompanied by decreased renal function characterized by inability to concentrate the urine and low corrected creatinine clearance. The treatment with saline infusions and furosemide was usually effective.