This article reports on a study of the disposition of loading doses (1g and 15 mg/kg) of vancomycin given intraperitoneally to 6 patients on continuous ambulatory peritoneal dialysis with Gram-positive peritonitis. Dialysate samples were collected every 30 minutes during the first dwell, and serum samples were collected after the first 5 exchanges and after 7 or 14 days. The dialysate concentration/time data were fitted to a monoexponential curve for 4 patients and to a biexponential curve for 2 others. Dialysis clearance was 0.73 ± 0.04 L/h (1g dose) and 0.70 ± 0.23 L/h (15 mg/kg dose). Total body clearance was 0.51 ± 0.36 L/h. Serum concentrations reached 14 to 18 mg/L (15 mg/kg dose) and 6.75 to 24 mg/L (1g dose) at the end of the first dwell. The half-life of equilibration of vancomycin across the peritoneal membrane was 2.5 ± 2.3 hours. Intraperitoneal loading doses of vancomycin produce concomitant serum concentrations in excess of the minimum inhibitory concentrations for susceptible organisms. Administration on a milligram per kilogram basis produces more consistent serum concentrations than using a standard loading dose which is not based on bodyweight.