Evidence-based medicine is the explicit use of the currently best available scientific data for decision-making in the management of individual patients, with guidelines being among the instruments for its implementation. Publication of the German S3 guideline on the treatment of plaque-type psoriasis is a mile-stone for German dermatology, as it is the first dermatologic guideline at this highest level of evidence. Standardized analyses of the respective publications provide the basis for this guideline. This article explains the principles of such an analysis, so the reader can gain insight into the methodology of a crucial aspect of guideline generation. This information is of general relevance, as it provides help for every physician who wishes to critically read original scientific publications.