In this article, we present grammatical forms of peripheral types of substantive declension, observed on the material of the largest Old Russian chronograph of the 15th c. — The Hellenic and Roman Chronicle of the 2nd recension. Thematic diversity and vastness of the text provide a lexical wealth of material: approx. 4,500 nouns in 35,000 uses. This seems particularly significant when studying peripheral declension types. Thus, in the text, almost all the words belonging to the declension in *-es are marked, and in all case-numerical forms. The genre specificity of The Hellenic and Roman Chronicle presents such lexemes in the contexts diverse in content and structure. This highlights the beginnings of a stylistic differentiation of grammatical forms that sometimes accompanies their historical changes, as well as semantic support for grammatical and phonetic reasons for the disappearance of the old declension types. For example, the analysis of the thematic group of the names of the cubs recorded in The Hellenic and Roman Chronicle has confirmed that the destruction of the declension type with the ancient base in *-ęt was promoted by the small number of the lexemes included in it, formed also by the word-formation variability of the meaning ‘non-adulthood.’ The text is a compilation of large and small fragments from a variety of sources dating 10th–15th c. They retain in most cases the morphological forms of the texts used, so the language of the Chronicle reveals different grammatical variants at different times. A study of nouns on the material of The Hellenic and Roman Chronicle helps, in particular, in stating that before the distribution of nouns according to productive types of declension, there was an opposition of singular and plural forms in them. One such mechanism of opposition, particularly for the ancient consonantal declension, was the long retention of the two types of base.