The meta-analysis of randomised controlled studies (RCS) achieves the highest degree of reliability. Although the status of prospective multicenter clinical trials (PMS) is the subject of controversial discussion, recent publications suggest that these two forms of analysis reveal comparable results. On the other hand, particularly in the operative part of medicine, the problem of recruitment and performing of controlled studies for the more rapid evaluation of new surgical procedures becomes more evident. We followed these two aspects by using a separate analysis of data and biostatistical models. In the evaluation of single aspects, under no circumstances can non-controlled clinical trials replace randomised clinical studies in surgery. Only the use of a variety of forms of analysis in clinical research will lead to the desired scientific findings.