The letters written in the papal chancellery during the reign of Saint Gregory the Great (590-604) are the most important source of both secular and ecclesiastical history of that time. They were copied and preserved in the papal records in annual papyrus books, which we call Gregory's Registrum epistularum. The papyrus books have been lost, but before that excerpts had been made during the eighth century. These excerpts were successfully used to reconstruct as much as possible of the original Registrum in the last text edition, published between 1887 and 1899 by P. Ewald and L.M. Hartmann in Monumenta Germaniae Historica. This was in many respects an important work.
However, Ewald and Hartmann were primarily historians and were not able to study in detail the relationships between, and value of, the manuscripts. Moreover, new manuscript witnesses have come to light, the study of the Latin language of late antiquity has made rapid progress and new tools, like e.g. the Thesaurus linguae Latinae, have emerged. This new edition therefore aims to meet modern expectations. The reconstruction of the Registrum on the whole is the same as before, but at several points the text has been adapted to the results of recent scholarship.