The clearance of vancomycin during therapy with continuous arteriovenous hemodiafiltration (CAVHD) has been measured in vivo. Vancomycin clearances (n = 16) were 0.636 +/- 0.269 L/h (10.5 +/- 4.46 ml/min). Effective drug clearances were proportional to ultrafiltrate volumes, reflecting convective clearance. Clearances of vancomycin on CAVHD were approximately twice the values seen with continuous arteriovenous hemofiltration. These data allow construction of a dosing schedule for vancomycin therapy in patients receiving renal support via CAVHD.