This study was devised to identify sepsis-relevant parameters that early and reliably predict a lethal outcome in intra-abdominal sepsis. In 18 Duroc pigs, peritonitis was induced through standardized gastrotomy. Twelve hours later the defect was oversewn and the abdominal cavity lavaged thoroughly. Sepsis relevant parameters were measured before initiating therapy, and 30 min later animals were extubated and observed for a period of 6 days under adequate analgesia with free access to water and food. All parameters were correlated with survival postoperatively. In the treatment group, 7 out of 18 pigs (39%) died within the observation period. Endotoxin level at 30 min after initiation of therapy [17.9 EU/mL ( - 12.1) vs. 110.9 EU/mL ( - 21); p < .001] and j pHi [0.015 ( - 0.011) vs. m 0.039 ( - 0.013); p = .016] were identified as the two parameters with highest predictive power regarding mortality in a multivariate analysis. In conclusion measurement of endotoxin and gastric tonometry should gain wider clinical application in septic patients.