Treaties of Russia and Byzantine and the Social Upper Layer of the Russian Society of the X Century (Towards Formulation of the Problem). The article is dedicated to studying Russian-Byzantine treaties, the texts of which are placed into the most ancient Russian annals «Povesti vremennih let» under the years 907, 911, 944 and 971. These treaties represent the most ancient written records that reflected the reality of the early medieval state of the Kiev Russia. Despite the editorial proof-reading at the composition of the annals, the given treaties offer the information that is prior to the content of the annals into which they were included later. The author of the article analyses the structure of personal names that were included into the treaties from the Russian side. The majority of these names are of the Scandinavian origin. There are only three authentic Slavonic names. These are the people who can be considered the heirs of Rurik. All the people mentioned in the texts of the treaties are representatives of the nobility of Varangian origin. They have no relation to the chieftains of the Slavonic tribes subordinate to Kiev. Basing on the analysis of the text of the treaties the author follows the changes in the social structure of the upper layer of the Russian society in the X century.