ENAn investigation into both lexis and phraseology of the East Slavonic languages of the period of their formation is of great importance for the historical lexicology. The object of research of this article is the formation of set phrases of the terminological character in the three editions of the Statute of the Grand Duchy of Lithuania, 1529, 1566, 1588. The aim of the present research is a description and analysis of set phrasal units, their semantics and structure. As far as the constitutives of the set phrases are concerned, the structure of the largest group of the terms is: noun+adjective (in grammatical agreement) used either prepositionally or, most often, postpositionally. In such nominal phrases the core constituents very often are Old Russian polysemantic words or, in a number of cases, foreign words, most often Polonisms. The basic words and their attributives ñ adjectives, as a rule, make up two-component phrasal units, they function as terminological units and belong to different thematic groups. Another structural model rather frequently occurring in the Statutes is a unit of verb+noun in various transpositions of the components. In the course of the comparative analysis of the texts of the Statutes it has been discovered that in the set phrasal units the same verbs recur, however, in combinations with different nouns. In the article, apart from the above indicated aspects of the set phrasal units, the synonymy of the phrases has also been investigated.