Summary The hemodialysis clearance, total body clearance off dialysis, and protein binding for theophylline were determined in a 64-year-old cigarette-smoking male in acute renal failure. The hemodialysis clearance of 39.4 ml/kg/hr was comparable to two other reports and indicated that theophylline was significantly hemodialyzed. The total body clearance of 52.4 ml/kg/hr was similar to that observed in non-renal-failure smoking patients and suggested that renal failure did not appreciably affect the total body clearance in the patient. The plasma protein binding was 40% before dialysis and 33% after dialysis. This finding implied that renal failure and hemodialysis may alter protein binding compared to that in normal adults. Theophylline plasma levels should be monitored in renal failure patients because the drug is hemodialyzed. Decreased plasma protein binding may indicate the need for a lower therapeutic range in this patient population.