ENThis article discusses the characteristic of ŏ-stem nouns in the 16th-century monument of writing belonging to the first Belorussian-Lithuanian compilation. The purpose of the article is the analysis of the declension of masculine and neuter nouns with regard to alterations in comparison with general Old Russian. The most crucial phenomena which are confirmed in the Supraśl Chronicle are: a tendency to inter-declensional leveling and within the ŏ-declension itself. It leads to an increase in the number of endings of the same case as well as fluctuations in their usage. In the Supraśl Chronicle residual forms of the dual number can be observed. In most cases they were leveled to the plural number. The text is also characterized by the inconsistent usage of the animacy category.