Despite all the efforts made in the areas of intensive care and surgery, severe peritonitis remains a feared condition that is associated with a high mortality rate. Severe abdominal infections are accompanied by a high level of endotoxin production, resulting in the so-called systemic inflammatory response syndrome (SIRS), which is often complicated by multiple organ failure. In addition to the surgical elimination of the source of the infection, the removal of the endotoxin is of prime importance. The aim of surgical treatment of peritonitis is, in the first instance, the elimination of the bacterial contamination and prevention or reduction--if possible--of fibrin formation. Attempts to block the cascade of mediators by pharmacological means have so far proved ineffective. For more than 10 years, therefor, various forms of abdominal lavage have been of vital importance in reducing bacterial contamination and aiding the healing process after successful surgical elimination of the focus of infection. A watertight temporary closure for the abdominal wall (TAC) was developed, which makes possible the continuous irrigation of the abdominal cavity. At the same time, it also gives the oedematous abdominal organs room to expand without the constraints otherwise imposed by the abdominal wall. This concept has extended the spectrum of surgical options, and we believe that, as a result, a reduction in the mortality rate associated with severe peritonitis with sepsis (MPI > 26) can be achieved. To investigate this hypothesis, a multi-centre study is presently being conducted. In a prospective parallel-group study, patients are randomized to either programmed etappenlavage with the Ethizip or to open dorsoventral interval therapy using the TAC. The patients are stratified on the basis of APACHE II and MPI, and the post-operative course is documented in a standardized manner. As secondary objectives, the study also aims to clarify the question as to whether the new therapeutic concept is also capable of reducing the number of revisions necessary, the duration of intensive care treatment, and the lenght of hospitalization, as also of abbreviating antibiotic treatment. Since it is being done under controlled conditions, and a uniform documentation is being used, the study represents a major contribution to quality control in the field of surgical treatment of peritonitis.