Memoirs of ordinary and professional revolutionaries of Siberia, previously not widely involved in scientific use, compose the subject of the paper . The purpose is to attract the attention of researchers to the historical sources under consideration (ego-documents on the history of the revolutionary movement of the end of the XIX – early XX centuries, the October Revolution and the Civil War, kept in the collections of the Siberian Historical and Party Commission (Sibistpart) of the State Archive of the Novosibirsk region P–5), as well as to confirm their high research potential. There are considered the activities of the Siberian Istpart as a new center for the development of historical science and the main collector and publisher of valuable ego-documents, the features of the revealed memories as a historical source and the specifics of working with them; the analysis of some memories is given to test the methods of such work. The research methodology includes the discourse analysis, biographical approach, and the method of source studies. The study of the P–5 collection materials has made it possible to classify the entire collection of memories gathered by the Sibistpart due to the level of the authors’ literary professionalism and the nature of the content; to identify the features of the memoirist’s linguistic style and thinking; to highlight the subjects paid more attention to – therefore described in detail and given his own opinion – to outline further prospects for studying these ego-documents. Conclusions are made about the high information value of these historical sources, and possible thematic and methodological directions for working with memoirs of the first half of the XX century are proposed.