Open management of the peritoneal cavity with mesh insert in severe peritonitis has been the subject of favorable clinical reports. The present study was undertaken to develop an animal model suitable for investigation of this technique. Peritonitis was induced in anesthetized rats using the technique of cecal puncture following nonobstructing cecal ligation. A pilot study with this technique did not result in either intestinal distention or edema. Therefore, distal ileal ligation was added to duplicate the clinical findings associated with diffuse peritonitis. Twenty animals treated in this manner underwent standard abdominal wall closure and were simply observed for 96 hours. This produced a 15 per cent mortality at 24 hours, 65 per cent at 48 hours, 70 per cent at 72 hours, and 80 per cent at 96 hours. A second group underwent sham laparotomy only (n = 5) with a resultant 100 per cent survival. Based on these preliminary findings, two study groups were defined. Animals in both groups had cecal ligation and puncture and ileal ligation performed. Group I (n = 22) animals underwent re-laparotomy 24 hours later with primary fascial closure, while group II (n = 23) animals underwent re-laparotomy at 24 hours with placement of a standardized Dexon mesh insert covered by a superficial polyethylene film to prevent fluid loss. No animals received antibiotics. Cumulative mortalities in group I were 77, 90, 90, and 90 per cent at 24, 48, 72, and 96 hours after reoperation. In group II mortalities were found to be 48, 57, 61, and 70 per cent at 24, 48, 72, and 96 hours.(ABSTRACT TRUNCATED AT 250 WORDS)