ENThe long neighborhood of two neighboring state formations: the Grand Duchy of Lithuania and the Moscow State led to a constant interpenetration of representatives of local service elites. This process had a different degree of intensity, intensifying during military clashes and internal political conflicts. One of its results was the emergence in the Moscow service of an impressive number of «Litvins», the process of integrating which into the existing system of official relations and into the social environment of local serving communities of the 15th–16th centuries are the subject of research of the article. [From the publication]