[The unknown acquaintance, or the impact factor and others].

Nobody doubts the importance of the scientific performance's evaluation. At the same time its way divides the group of experts. The present study mostly deals with the models of citation-analysis based evaluation. The aim of the authors is to present the background of the best known tool - Impact factor - since, according to the authors' experience, to the many people use without knowing it well. In addition to the "non-official impact factor" and Euro-factor, the most promising index-number, h-index is presented. Finally new initiation - Index Copernicus Master List - is delineated, which is suitable to rank journals. Studying different indexes the authors make a proposal and complete the method of long standing for the evaluation of scientific performance.