Secondary peritonitis is associated with a high mortality and morbidity. Besides adequate antimicrobial therapy and resuscitation, surgical intervention is the cornerstone of the treatment of these often severely ill patients. Antifungal prophylaxis is advised for patients who have a high risk of developing a fungal infection. Extensive lavage of the peritoneal cavity after elimination of the intra-abdominal infectious focus has no demonstrable positive effect and can even be harmful. A randomised clinical trial showed that relaparotomy on demand (ROD) after the first surgery is the preferred treatment strategy in the case of clinical deterioration, irrespective of the severity of disease. The effective and safe use of ROD requires intensive monitoring of the patient in a setting where diagnostic tests and decision making about relaparotomy are guaranteed around the clock. A reduction in the mortality and morbidity associated with secondary peritonitis can be achieved with a multidisciplinary approach involving more extensive diagnostic and decisional support.