The aim of this study was to evaluate the effects of planned relaparotomy and to assess factors that may contribute to mortality in patients with moderate to severe secondary peritonitis. A total of 36 consecutive patients with an Acute Physiologic and Clinical Health Evaluation (APACHE) II score of >10 were enrolled the study for a 2-year period. The mean age of the patients was 56 years (17-92 years), and 23% of them were male. One-third of them had postoperative peritonitis; 152 scheduled operations were done, and the overall mortality rate was 36%. For patients whose septic source was in the upper gastrointestinal system, control of the source was more difficult (p = 0.004). Overall, 28 complications developed in 61% of the patients. Initial and second-day APACHE II scores were 14.5 (11-27) and 12.0 (9-25), respectively. The initial APACHE II score of survivors was lower than that of nonsurvivors [p = 0.0001, 95% confidence interval (CI) -9.5, -3.6]. Second-day APACHE II scores were not different (p = 0.19; 95% Cl -3.79, 0.80). Striking end or lateral duodenal leaks were clearly associated with high mortality. It is found that the initial APACHE II score, the success of controlling the source, the occurrence of complications, and the type of illness are independent factors that may affect mortality. We concluded that staged abdominal repair should be used with caution in the treatment of lateral or end duodenal leaks. It is a good alternative to conventional laparotomy for moderate to severe forms of secondary peritonitis from other sources.