The article contains the text of the source, described the Eastern Transbaikalia and the Amur River. It was compiled in 1681 in Moscow by the regional administrative office Sibirsky Prikaz, based on the testimony of Siberian Cossacks. Compared to other previously published documentary and narrative sources, this description provides more detailed information about the above-mentioned specific region, including its natural resources, the location of Russian settlements; the number, living conditions and armament of the Russian population; land and river routes, habitats, lifestyle and the degree of loyalty of the local people toward the Russian authorities, about the relationship between Russians and “Chinese people”. The source is stored in the Russian State Archive of Ancient Acts (Moscow) in the collection of documents from Sibirsky Prikaz.