The reissue of the letters of St. Jerome, which is complemented by indices, represents the first volume in a revised edition of the famous series CORPUS SCRIPTORUM ECCLESIASTICORUM LATINORUM (CSEL). This collection of St. Jeromes Epistulae, the only complete edition of this work, includes not only the Latin texts but also offers an overview of scholarly research concerning texts and sources. This has been achieved by reproducing the original text of the three volumes edited by Isidor Hilberg in the years 1910 to 1918 without alterations, while also marking all passages for which emendations to the text and new findings appertaining to sources have since been published. These can be verified with the help of the newly-compiled volume containing the exhaustive indices, which include the index criticus, reference lists of Bible quotations, quotations from Classical literature, proper names, the recipients and authors of the letters, as well as the manuscripts. This method of presentation facilitates an intensive reading of the epistulary corpus of this Father of the Church and is intended to provide a solid basis for future philological and theological research as well as research in ecclesiastical and social history.