Fourteen episodes of peritonitis complicating chronic peritoneal dialysis were treated with intravenous injections of 1 gm of vancomycin weekly for 4 successive weeks. Peak (one hour after completion of injection) and trough (immediately before the next injection) serum and dialysate vancomycin levels were measured. Vancomycin treatment resulted in a cure in 12 episodes (85.7%). Serum vancomycin levels were always above therapeutic range, but did not rise, with subsequent injections, to toxic range. Dialysate vancomycin levels were therapeutic for more than 85% of the measurements. One patient, who failed to respond to vancomycin plus cephalosporins, was cured with intraperitoneal streptokinase plus the same antibiotics. In another patient, a relapse was cured with vancomycin plus oral rifampin. Dialysate vancomycin levels were therapeutic in the last two patients. Peritoneal catheters were not removed. No significant side effects of vancomycin treatment were observed.