The article, based on archival documents, shows the role of Professor E. G. Kagarov (1882-1942), an outstanding ethnographer and historian of religion, in creating the theoretical and methodological grounds for the expositions of the Museum of the History of Religion of the Academy of Sciences (1932). Kagarov was of similar minded to V. G. Bogoraz and was his close collaborator in the creation of the Museum as a new academic institution. Of course, Kagarov attracted Bogoraz not only by his encyclopaedic knowledge, but also by using in his works new methodological approaches in comparative religious studies as it was rapidly developing in Europe and Russia at that time. Kagarov's views on mythology and religion, on approaches to the interpretation of sources, as well as on what could serve as a source for the study of ancient religions, differed significantly from the generally accepted ones and went beyond the narrow textual studies accepted in philological tradition. His appeal to the comparative method, the involvement in folklore and ethnography data for the analysis of ancient religion, was innovative for the domestic science. Kagarov believed that, beginning in the second half of the 19th century, in Western Europe the history of religions became an independent discipline, free from confessional frameworks. In Soviet Russia that academic science used "economic materialism" as a method of historical knowledge, treating religion as a reflection of production relations, conditioning the social and political system. The article is accompanied by the publication of the annotated list of works on the history of religion by E. G. Kagarov from the B. G. Bogoraz collection in the St. Petersburg branch of the Archive of the Russian Academy of Sciences. Refs 8.