Prolongation of neuromuscular block following pancuronium administration to anephric patients has been reported. A patient is described whose postoperative course after resection of gangrenous bowel was complicated by acute renal failure and prolonged neuromuscular blockade. A large intraoperative dose of pancuronium was administered without monitoring neuromuscular transmission with a peripheral nerve stimulator. The course was further complicated by administration of gentamicin, an antibiotic known to potentiate neuromuscular blocking drugs. Complete return of neuromuscular transmission occurred 60 hours after administration of last dose of pancuronium and subsequent to peritoneal dialysis. After rapid distribution from plasma, pancuronium, like curare, is eliminated by the renal pathway. The absence of renal excretion considerably increases the duration of action of curare when given in high doses. It has been suggested that doses of pancuronium greater than 3.6 mg/sq m or multiple doses would result in prolonged neuromuscular block in patients without renal function. The case reported illustrates the importance of monitoring neuromuscular transmission during administration of pancuronium in the presence of renal insufficiency to avoid this complication.