Calcium channel blocker therapy has proved protective in certain models of ischemic-induced acute renal failure. This effect may be related to the prevention of calcium influx into injured cells or by the vasodilatory effects of verapamil that may result in an improvement in renal blood flow. In the current study, the effect of verapamil treatment on the development of renal insufficiency and renal tissue calcium accumulation following aminoglycoside administration was investigated. The degree of functional damage and cortical tissue calcium accumulation after six or nine days of gentamicin administration (120 mg/kg body weight/day) was not significantly different in rats whose drinking water contained verapamil (10 mg/100 cc) than corresponding values in control animals. The tissue calcium accumulation correlated with the degree of reduction of creatinine clearance and probably reflects the extent of lethal tubular cell injury.