Abstract The Upper Proterozoic of the U.S.S.R. is subdivided into two chronostratigraphic units according to the officially-adopted stratigraphic scale: the Riphean, 1650 ± 50−650 ± Ma, comprising four subordinate subdivisions; and the Vendian, 650 ± Ma—Cambrian. The lower boundary of the Riphean is drawn on the top of late volcanogenic molasse of Svecofennian (Hudsonian) age, and that of the Vendian at the base of Laplandian glaciohorizon. The boundaries of the four subdivisions of the Riphean, i.e. the Burzyanian (1650 ± 50–1350 ± 50 Ma), the Yurmatinian, (1350 ± 50−1000 ± 50 Ma), the Karatavian (1000 ± 50—ca. 680 Ma) and the Kudashian (ca. 680-650 ± Ma), are defined by orogenic breaks and/or paleontological criteria (stromatolite and microphytolite assemblages). The type sections of the Riphean and its four subdivisions are located in the southern Urals. The isotopic ages of their boundaries are generally based on K-Ar dates on glauconite supplemented by a few Rb-Sr, U-Pb and K-Ar ages from associated volcanics and plutons. The type section of the Vendian is located in the western part of the Moscow syneclise and starts with two continental tillites; above the tillites in several regions of the Eastern European platform there appears a diverse assemblage of the Ediacara-type fauna. The above subdivisions of the Upper Proterozoic are traced in the main key sections of the U.S.S.R., using available biostratigraphic, radiometric and lithostratigraphic data. A brief description of the type and key sections is given. These chronostratigraphic subdivisions of the Upper Proterozoic of the U.S.S.R., which are well documented by stromatolites and microphytolites, have been recently identified in other continents, especially in Australia and Africa.