The removal of phenytoin by hemodialysis was determined in seven uremic patients. Four patients were receiving phenytoin sodium for therapeutic purposes; three received one dose each intravenously to quantitate its disposition in uremia. The drug was measured in whole blood, plasma, saliva, and dialysate. Only 2% to 4% of the intravenous dose was recovered in the dialysate. Phenytoin clearance by dialysis was 7 to 14 ml/min; plasma clearance was 53 to 133 ml/min. Since hemodialysis contributes little toward shortening to 11-to-18-hour half-life of phenytoin in the uremic patients, no supplemental dose is necessary for uremic patients undergoing hemodialysis.