The stratigraphy, sedimentology and palaeogeography of the Cenozoic filling of the basins in the Eastern Siberia rift system are described. A regional scheme for the stratigraphy of the Cenozoic sediments is proposed with special attention being paid to the processes of ancient weathering. The sedimentation is divided into stages which differ in tectonic pattern and climatic conditions. At the Late Cretaceous - Early Paleocene boundary, lateritic weathering residues were developing in the Sayan-Baikal highlands, in a stable tectonic environment under a warm moist climate. During the second stage, through most of the Paleogene and Early Neogene, a coal-bearing molasse accumulated. The third stage covers the deep-lake sedimentation in the Baikal and Khubsugul basins, which began in the Pliocene and is continuing at present.