Prolonged postoperative peritoneal lavage has been used as a part of the management of 55 patients with diffuse peritonitis. The lavage technique consisted of 60 min cycles of instillation and drainage of a lavage fluid into the peritoneal cavity via a peritoneal dialysis catheter. The lavage fluid was a slightly hypertonic salt solution containing antibiotics, usually cefotaxime and metronidazole. The overall mortality rate in the series was 11% (6/55). Only one of these patients had residual abdominal sepsis present at post-mortem, the remaining deaths being due to a progression of the pre-existing disease. Five patients showed evidence of further intra-abdominal sepsis. In three of these patients this was associated with the presence of a previously well established abscess cavity. The overall results indicate that, for this group of patients recognized to be at high risk of mortality or further sepsis, the use of prolonged postoperative peritoneal lavage is associated with an improved outcome.