The employment of the optimal therapeutic option according to the best current knowledge is called evidence-based medicine (EBM). Moreover, considering the cost explosion in public health systems, EBM should contribute towards economical and targeted use of the restricted resources and towards quality assurance in medicine. Obviously, this is applicable to the operative specialties and can be termed as evidence-based surgery. Surgeons have to do their "homework" about this subject and to perform randomized controlled trials (the gold standard with the greatest evidence) on a large scale, in order to come up to this expectation in future. Evidence-based therapy is essential for the preservation and especially for the further development and evolution of high-quality surgery with, at the same time, quality assurance in the new millenium. This article presents the definition of EBM and its implication in the operative fields. Fundamental principles for the practical conduct of clinical randomized controlled trials are defined and the specific problems in surgery are discussed.