[Necessity and field of application of retrospective analyses in a time of prospective controlled studies (author's transl)].

Prospective controlled studies give the most reliable background for clinical decisions. To use them correctly, however, many strict premises have to be fulfilled that are often impossible in practice. If no research is conducted in these cases, however, that means disastrous dependence on one method. The main application of retrospective analyses is therefore in the sense of a second-best solution. Furthermore, retrospective consideration is a genuine necessity for medical research if you are interested in the critical reflection of your own work and in dealing with new problems.