This report describes the development of a rat peritonitis model that simulates a slow, sustained bacterial release from the gut. Septic animals (SEP) received an intraperitoneal infusion of a bacterial inoculum (6.5 x 10(8) colony forming units Escherichia coli) over 12 h, while control rats (CON) received a sterile inoculum. This model yielded a 52% mortality over 7 days in SEP, with deaths usually occurring 24-48 h after the onset of infusion. Septic rats showed greater febrile responses and body weight losses than those of CON, as well as mild hyperlactacidemia, hypoglycemia, and episodic bacteremia. Maximum bacterial counts in peritoneal fluid and several organs of SEP were observed at 36 h, with bacterial counts progressively decreasing by 7 days to levels similar to those observed at 12 h. Lung and spleen wet weights increased by 17% at 36 h and 7 days post-infection in SEP. Histological evaluation of random organ samples revealed mild to moderate morphological changes in SEP while CON showed no or minimal changes in the parameters measured during the study. This new model of chronic peritonitis in the rat reproduces many of the clinical features observed in human sepsis, and thus should prove to be a useful tool in further studies of the pathophysiology of peritonitis.