Peritonitis was induced In 12 dogs by creation of an avascular jejunal loop. After 24 hours, the avascular jejunal loop was removed, and purulent material was removed by aspiration. The abdominal incision in six experimental dogs was left open under a bandage, while the incision was closed in six control dogs. All six open abdomen, and four control, dogs survived the 8 days of the study. The number of bacteria in the peritoneal exudate in experimental animals was less than in control animals. At the end of the 8 day study, experimental animals were more active, had better appetites, and were less likely to have fever, vomition, diarrhea, and dehydration. Experimental animals weighed significantly less than control animals. There were no differences between groups with respect to biochemical and hematologic parameters. At necropsy, experimental animals had fewer adhesions and less peritoneal fluid accumulation than control animals. Complications of open peritoneal drainage included persistent fluid loss, weight loss, adhesions of abdominal viscera to the bandage, and contamination of the peritoneal cavity with cutaneous organisms.