This lecture covers the issue of Slavonic tribal unions in the social and economic aspects. The patterns of power organisation within the tribes are studied, the problem of the social and economic history of Kievan Rus' is brought forward for discussion. The picture of Christianisation of Kievan Rus' is drawn. The first Russian princes (knyazes) such as Svyatoslav, Yaropolk, Vladimir I of Kiev, and Yaroslav the Wise are given an account of.