Hypercalcemia developed in a man with recurrent adenocarcinoma of the prostate. Serum calcium became normal soon after bilateral orchiectomy and the patient was free of disease 18 months later. The absence of radiographically detectable bone metastases in this patient suggested a humoral mechanism for the hypercalcemia. Orchiectomy may be an effective treatment for hypercalcemia complicating prostatic carcinoma.