Severe cases of pseudomembranous colitis (PMC) may be associated with intraperitoneal fluid accumulation. However, the characteristics of the liquid are seldom described. Specifically, neutrocytic ascites has only been reported once. We report a case of a severe PMC complicated by a highly neutrocytic ascites which remained culture-negative. We discuss the possible mechanisms leading to ascites formation in this condition and review ascitic fluid characteristics in patients with PMC.