In making available to the general public the manuscript of the Slavonic-Latin Liturgy of St. John Chrysostom, the original of which is to be found in the Byelorussian Library of Francis Skaryna in London, we hope to acquaint a wider circle of liturgists with an authentic text of the pontifical celebration of the Divine Liturgy and its ceremonies which were celebrated according to the order (ustau) of the Eastern Catholic Church of the Metropolitan See of Kiev and of the whole “Ruthenian land” in the sixteenth and seventeenth centuries. This edition seeks to be one more concrete illustration of the Pontifical Liturgy preserved in the manuscript of the Byelorussian Library (referred to hereafter for convenience as MS BL), which, although it has many things in common with those already known through various publications, still has its own particular merit for Byelorussians and Ukrainians.