Introduction. The introduction of new sources characterizing traditions of Buryat chronicle writing into scientific circulation remains an urgent task of Mongolian studies. Dozens of works and their various copies and editions are still there to be explored. The article precedes a further study and translation of a voluminous historical chronicle of the Aga and Khori Buryats. Goals. The study attempts a brief overview of the chronicle’s contents and approaches some peculiarities traced in its text. Materials and methods. The analysis of Rabzhi Sanzhiev’s writing involves a wide range of Buryat historical works — both chronicles and archival documents. The historical comparative and chronological methods prove instrumental in systematizing the data contained, while tools of textual and source studies have made it possible to delineate the author’s text proper. Results. The work identifies an extensive range of sources and the chronicle’s structure according to which R. Sanzhiev’s narrative be conventionally divided into a number of large sections, namely: Shirab-Nimbu Khobituev’s chronicle; copies of official documents; historical works by T. Toboev, D. Zayaev, S. Vandanov, A. Ochirov; and the author’s text. Conclusions. R. Sanzhiev’s writing is a major work of the historical documentary genre. The author undertook painstaking efforts to meticulously clarify data included in Shirab-Nimbu Khobituev’s chronicle and supplement certain facts and data, introduce additional findings from various sources. The continuation of Khobituev’s chronicle — despite the compiled facts are fragmented enough — acts as an independent composition. Archival documents on the history of Buryat self-governance and Buddhism, folklore texts, chronicles and legends included by the author into the narrative are of particular value.