Volumes 4 and 5 of the Library of Early Christianity, The Correspondence of Theodoret of Cyrus: The Collectio Sirmondiana, present a text and translation of the largest of three collections of Theodoret's letters that have come down to us (first edited by the Jesuit father Jacques Sirmond, Paris 1642). Though pastor of the remote see of Cyrus in Syria, Theodoret was one of the major teachers of the eastern Christian church of the late fourth and early fifth century.

These 147 letters place before us the myriad concerns, both spiritual and secular, of a late-antique bishop: Theodoret expounds theological and moral issues for fellow churchmen, begs imperial officials for tax relief for local landowners, provides for the sustenance and safety of refugees from the Vandal war in Africa, thanks a friend for a gift of wine. The edition of the Greek text is the work of John Petruccione. A textual introduction explains the relationships among the manuscripts, and the critical notes the choices made where the text is uncertain. The historical / theological introduction is the work of István Pásztori-Kupán, one of the foremost expositors of the thought of Theodoret and of his Antiochene predecessors and contemporaries. Two maps locate for the reader the place names mentioned in the letters, and three indices (a Scriptural Index, General Index, and Index of Modern Authors) complement the notes attached to the text and translation.