Abstract: Malignancy-induced hypercalcemia is treated with thionapthene-2-carboxylic acid (TNCA) and the pharmaceutically acceptable salts thereof. The treatment is also effective in tumor bearing hosts even before there is significant abnormal serum calcium levels. There is no "escape" from the hypocalcemic effects of these compounds as with e.g., calcitonin. The useful dosage in humans for TNCA itself ranges from about 1 to about 60 mg/kg/day preferably from about 2 to about 30 mg/kg/day and more preferably from about 5 to about 20 mg/kg/day (20 mg is approximately 0.106 mmol) Orally administered TNCA or salts thereof, is a much desired and obviously clinically advantageous mode of administering compounds to control or ameliorate hypercalcemia.