In this open-label study, the authors assessed the pharmacokinetics and safety of ibandronate in patients with multiple myeloma and varying renal function. Renal deterioration was graded at baseline depending on creatinine clearance in 4 stages (0: >80; 1: 50-79; 2: 30-49, and 3: <30 mL/min). Patients (n = 40) received intravenous ibandronate 6 mg (30-minute infusion). Ibandronate excretion and serum levels were measured over 24 hours. Serum creatinine, creatinine clearance, and markers of tubular damage were monitored before ibandronate infusion and at 24 and 72 hours following ibandronate infusion. Ibandronate clearance, AUC(0-24), AUC(0-infinity), serum t((1/2)), and C(max) were calculated. There was a significant positive correlation between ibandronate clearance and creatinine clearance (r = 0.858; P < .00001). The AUC for grade 3 renal insufficiency increased by approximately 60% versus grade 0 (P < .01) but was not significantly different between other grades of renal function. The t((1/2)) did not increase significantly, and peak serum levels of ibandronate were similar for the 4 grades of renal function. Serum creatinine, creatinine clearance, and markers of tubular damage did not change significantly within 72 hours of ibandronate infusion. Despite renal function already being compromised in this patient group, there was no evidence of acute nephrotoxicity with ibandronate.