In 2004, the authors first developed and implemented a regional external quality assessment program (REQAP) for the diagnosis of syphilis in the Volga Federal District (VFD). Its objective is to improve the quality of studies in the clinical laboratories of AIDS prevention and control centers (AIDS PCC) using a cardiolipin antigen precipitation microtest and/or enzyme immunoassay (EIA) for the diagnosis of syphilis and to compare the reproducibility of results at the laboratories. The program includes a theoretical stage--the issues concerning different aspects of the diagnosis of syphilis and the variants of replies to them; a practical stage--to solve enciphered problems, to draw up protocols; and a final stage--to sum up the results of two former stages and to organize a seminar. Twenty laboratories (16 laboratories of VFD AIDS centers and 4 laboratories of other therapeutic-and-prophylactic institutions) implemented REQAP for the diagnosis of syphilis. This resulted in the creation of a normative base regulating the techniques of diagnostic studies and appropriate test systems; revealed the sources of errors in the interpretation of the results obtained by the Lewis test; showed the correct interpretation of the results of EIA; indicated shortcoming when working with guide materials. Intralaboratory monitoring could reveal the incomplete realization of the stated sensitivity of test systems in considerable numbers of laboratories of the district, and well as no skills in statistical data processing. It is concluded that the normative base of diagnostic studies should be additionally worked over, that the laboratories should obligatorily participate in the Federal external quality assessment system, and that intralaboratory monitoring should be done. Most participants of REQAP for the diagnosis of syphilis are ready to use a precipitation microtest and EIA.