The article is devoted to the ornament and chronology of the Tanai culture and the characteristics of the inter-age transitional period in North-West Asia in the 2nd third of the 2nd millennium BC. The identification of the early Andronoid Tanai culture is substantiated, its area is outlined and an absolute chronology is established. The foundations of the typology of the Tanai ornamentation has been developed and its differences from the Korchazhkin decor have been traced. The sources of popular Tanai motifs, dating back to the Nurtai and Atasu antiquities of Central Kazakhstan, have been established. A suite of early Andronovo cultures, which constituted the historical content of the transitional period, is identified, and a series of dating confirming the unity of this cultural-chronological horizon is presented.