CO₂-pneumoperitoneum is known to favorably modify the systemic immune response in abdominal sepsis. We have shown that both CO₂-pneumoperitoneum and general anesthesia attenuate cytokine production and increase survival in septic rodents. We hypothesized that treating animals with CO₂ abdominal insufflation prior to undergoing a contaminated laparotomy would serve as “sepsis prophylaxis” and thus improve survival. Sixty-five rats were randomized into five groups (n=13): CO₂-pneumoperitoneum, helium-pneumoperitoneum, anesthesia control, laparotomy/LPS control and LPS only control. Animals in the first four groups all received a laparotomy contaminated with a lethal dose of intraperitoneal LPS (Escherichia coli, 10mg/kg). The LPS only control group received an intraperitoneal injection of LPS at the same dose. Immediately preceding their laparotomy, animals in the pneumoperitoneum groups received a 30-min pretreatment of abdominal insufflation (4 mm Hg) with either CO₂ or helium. The anesthesia control group received a 30-min pretreatment of isoflurane. Animal mortality was then recorded during the ensuing 72 hours. When compared only to LPS control, CO₂-pneumoperitoneum increased survival (69% vs 38%, p=0.06 via Kaplan-Meier Analysis). The survival curve for the anesthesia control group was not significant (69%, p=0.21). The helium-pneumoperitoneum and laparotomy groups resulted in intermediary survival (62%, p=0.21 and 54%, p=0.40, respectively). Furthermore, animals treated with CO₂-pneumoperitoneum exhibited fewer clinical signs of abdominal sepsis (e.g., piloerection, diarrhea). Abdominal insufflation with CO₂ prior to the performance of a laparotomy contaminated with endotoxin increases survival in an animal model. The beneficial immune-modulating effects of CO₂-pneumoperitoneum endure following abdominal insufflation. CO₂-pneumoperitoneum pretreatment may improve outcomes among patients undergoing gastrointestinal surgery who are at high risk for abdominal fecal contamination.