In the article the Serbian manuscript from Russian National library Gilf. 21 is described and its special significance among the Slavic service books is emphasized. According to the author, it reflects the new translations of services and prayers made at the beginning of the 13th century on the Mount Athos in the circle of the scribes of St. Savva Serbian. Since the end of the 13th century a number of these translations penetrate into Russia displacing and transforming the old successions that were common in pre-Mongol Russia.