Pamidronate (APD) is a drug widely used for the treatment of hypercalcemia of malignancy. Renal impairment has been associated with the use of other bisphosphonates in humans, and nephrotoxicity has been described after APD administration in animals. We retrospectively evaluated the safety and efficacy of APD administration in 31 patients with underlying renal insufficiency who received 33 courses of APD in doses of 60-90 mg. Hypercalcemia resolved or improved in 91% of the patients and only 1 case had severe hypocalcemia. A transient deterioration in renal function was observed in 8 courses but this was unrelated to APD administration. No systemic ill effects were observed. APD appears to be a safe drug in patients with underlying renal failure.