Hypercalcemia is an extremely rare complication of prostatic carcinoma. It occurs mainly in patients with disseminated osseous metastases and may be corrected by bilateral orchiectomy or hormonal manipulation. Humoral factors may be involved in its pathogenesis. Its occurrence is an ominous prognostic sign. We report a case of hypercalcemia that developed in a man suffering from adenocarcinoma of the prostate and who had undergone bilateral orchiectomy. Mental confusion, anorexia, and abdominal pains were the presenting symptoms. The hypercalcemia was refractory to treatment with fluids, furosemide, steroids, and calcitonin, and responded only to mithramycin. Cessation of this medication resulted in a prompt recurrence of the hypercalcemia.