The disposition of vancomycin was assessed in five patients receiving hemofiltration after intravenous dosing with an 18 mg/kg dose after a hemofiltration procedure. The serum concentration-time profile was characterized before, during, and after the next hemofiltration procedure. The t 1 2 of vancomycin was 136.0 ± 27.2 hours (mean ± SD) before hemofiltration and 4.1 ± 1.2 during hemofiltration. Approximately 400 mg of vancomycin was recovered in the filtrate and the hemofiltration clearance was 152.6 ± 21.5 ml/min. A significant relationship was observed between vancomycin clearance and ultrafiltration flow rate (r = 0.9914). A marked rebound in vancomycin serum concentration (52.4% ± 15.6%) was observed in all patients. Hemofiltration has a significant effect on the disposition of vancomycin. Because of the marked interpatient variability in elimination t 1 2 and the degree and time course of the rebound, an individualized approach to vancomycin therapy in this patient population is recommended.