Hypercalcemia is one of the most critical complications in patients with malignancy. We have used salmon calcitonin for treatment of hypercalcemia in these patients. The subjects were 49 hypercalcemic patients with various malignancies. Synthetic salmon calcitonin (SCT) was provided by Teikoku Hormone Mfg. Co. Ltd., Japan and 40 MRC units was administered twice daily i.m. or i.v. In 21 of 33 cases treated i.m. and in 8 of 16 cases treated i.v., a serum Ca decrease of more than 2 mg/dl was observed. The hypercalcemia was managed in 59% of patients within 6 days after initiation of the treatment and effective duration was 14 days. On the other hand, ineffective cases treated with a combination of SCT and glucocorticoid or SCT and mithramycin were managed in 57% and 86%. The 50% survival time was 69 days in the effective cases and 23 days in the uncontrolled cases (P less than 0.01). The main causes of death in the ineffective cases were renal insufficiency. On the other hand, in the effective cases, improvements of renal function were observed. The side effects were slight, and nausea and flushing were observed in 24% of cases. These data indicate that SCT is effective for lowering the serum Ca level in hypercalcemic patients with malignancies.