This volume contains a photoreproduction of the surviving parts of a manuscript written in Rus' ca. 1100 A.D. The main portion is in the library of the Monastery of St. Catherine at the foot of Mount Sinai, and a fragment is in the Leningrad Public Library. Any manuscript of this age is valuable for the information it provides about the language and culture of early Rus', but the significance of this combined codex is enhanced by the fact that it is the oldest representative of a special revision of the Psalter text which became standard in Rus' but not elsewhere in the world of the Orthodox Slavs. The volume also includes photoreproductions of portions of a mid-twelfth century Psalter from Rus' which is the second-oldest witness to this text.