Complicated intra-abdominal infections are an important cause of morbidity and may be associated with poor prognosis. The understanding of the pathophysiology of the peritoneum in the manifestation of abdominal sepsis and knowledge of the source of pathogenic organisms, which reach the peritoneal cavity, are crucial to the prevention of intra-abdominal surgical infection. The ability to identify the presence or absence of peritoneal inflammation probably has the greatest influence on the final surgical decision. This article reviewed the role and impact of the peritoneum in abdominal sepsis.