The pharmacokinetics of vancomycin have been studied in 4 chronic renal failure patients undergoing continuous ambulatory peritoneal dialysis. Patients received 1 g of vancomycin in 2 liters of dialysate during an initial phase, and serum and dialysate samples were collected for vancomycin determination. 54% of the amount introduced into the peritoneal cavity were absorbed systemically during a 6-hour cycle. Peak serum concentrations averaged 23.7 microgram/ml. Mean elimination half-life was calculated to be 66.9 h, and dialysis clearance averaged 2.4 ml/min.