Five episodes of fungal peritonitis were treated by intraperitoneal instillation of 5-flucytosine (5-Fc) while the patients remained on their usual schedule of dialysis. Therapeutic, nontoxic dialysate and serum concentrations of 5-Fc were achieved. Although some patients transiently responded with improved symptoms, a drop in their dialysate WBC count and negative cultures, all patients required removal of their dialysis catheters for cure. It is concluded that intraperitoneal (IP) 5-Fc, as used in this study, is not efficacious in the treatment of fungal peritonitis.