It has been previously reported that the most common cause of peritonitis in patients undergoing chronic ambulatory peritoneal dialysis (CAPD) is infection by a single gram-positive bacterial species. Polymicrobial bacterial infections are identified that may be secondary to bowel perforation. In 20% of cases bacterial cultures are negative. Although cultures may be negative when infection is due to a fastidious organism, when antibiotic therapy has been administered, and in cases of chemical peritonitis, a viral etiology should also be considered. We report the first documented case of herpes simplex peritonitis, which involved a 60-year-old female undergoing CAPD. Viral peritonitis may be an important form of peritonitis that has been previously unrecognized and should be considered in the differential diagnosis.