The therapeutic value of closed postoperative peritoneal lavage in perforated appendicitis with generalized peritonitis was assessed in a prospective, randomized study. In all patients the peritoneal cavity was irrigated peroperatively, and all received systemic ampicillin and tinidazole. The patients were randomly allocated to management with (n = 39) or without (n = 44) closed peritoneal lavage. Postoperative infection developed in ten patients of the lavage group and in four controls. The infection was intra-abdominal in one of the former and two of the latter cases. No intergroup difference was statistically significant. The lavage procedure had to be prematurely discontinued in ten cases. Closed postoperative peritoneal lavage is expensive and seems to involve a risk of complications. No clinical benefit could be attributed to the lavage in this series, in which the risk of overlooking therapeutic advantages was calculated as maximally 2.5%.