Randomized controlled clinical trials are the preferred scientific method and remain the vital bridge between basic science and improvements in health care according to general agreement. However, discussion has revealed various critical issues in the field of intraabdominal infection. Many of these critical points can be dealt with by prognostic scoring systems. In this paper the application areas for scores in clinical trials on intraabdominal infections are presented. These areas cover: assessment of severity of disease, definition of inclusion/exclusion criteria, analysis of comparability, adjustment for noncomparability, definition of end points and comparison of observed versus predicted outcome. The use of scoring systems in defining treatment policies is still experimental.