As part of the project "Papal Documents of the Early and High Middle Ages" of the Academy of Sciences in Gttingen, which is embedded in the overall undertaking of the Pius Foundation for Papal Document Research, the revised version of the Regesta Pontificum Romanorum is being created under the aegis of Klaus Herbers. The third volume builds on the first two volumes and contains the pontificates from Sergius II to Benedict VIII (from 844 to 1024). In short Latin regesta, contacts with the Pope are systematically explored in chronological order. By processing the history of research since the last edition in 1885, the number of entries for the almost 180 years of the third volume has been increased to over 3500. In addition to numerous new finds, letters to the Pope have now been included and narrative sources have been given greater consideration. The large number of surviving letters of Leo IV, Nicholas I and above all John VIII stand alongside the writings and deeds of almost unknown popes and anti-popes. Council acts and collections of letters and legal documents were evaluated, as were the episcopal lives of the Liber pontificalis and the most important historiography. The bibliographic update brought about a major step forward. The regesta refer to the editions that are authoritative today and the discussion about the authenticity and dating of the papal letters. Concordances and a register of initiates facilitate access.