Аннотация:The article is devoted to the history and formation of archival collections of Russian Orthodox abroad in domestic and foreign archives, manuscript departments of museums and libraries and other repositories. The main task of archival heuristics consists in developing a heuristic algorithm – a method of searching for primary sources on the basis of secondary information available in archival reference systems (NSA). Collections of documents acquire true importance only when information about them is available to historians, and they can be used in the interests of the evolution of scholarship. Bearing in mind the increasingly frequent requirement for researchers to use archival documents on the Russian Orthodox Church and the history of the Church Abroad, and also the interests of the evolution of church-historical scholarship, a good knowledge of the workings of archival reference systems (NSA) is essential. As a rule, researchers obtain information concerning the contents of collections of documents from inventories, reviews, catalogues, indexes, guides, and automated databases. As a result, the problem of the search for primary sources (documents) on the history of the Russian Orthodox Church cannot be solved without the knowledge and ability to orient oneself in archival referencing systems (NSA).