This volume analyzes the history of the Lithuanian Metrica—the chancellery books of the Lithuanian grand duke—from the formation of its books in the mid-fifteenth century until now. It reveals how the first Metrica books emerged in the second half of the fifteenth century, discussing the titles given to them in different periods in history, and explains why the Lithuanian Metrica should be considered the state archive of early Lithuania. Material hitherto unknown in academic literature about the fate of the Lithuanian Metrica at the end of the eighteenth century, in the last years of the existence of the joint Polish-Lithuanian state, is also revealed in this account. The book dedicates a great deal of attention to the history of the publication and research of the documents and books of the Lithuanian Metrica, which are now kept in Moscow, Russia, as a historical source.