The present volume of the history of medieval canon law contains two essays on late antique and early medieval papal letters: Detlev Jasper describes the history of the transmission and spread of papal decretals from the beginning of the fourth century to the end of the ninth century in the Latin West; Horst Fuhrmann tells the story of the Pseudo-Isidorian forgeries, a collection of conciliar decrees and papal letters that were arranged chronologically. The most influential and important texts in this collection were forged papal decretals that were attributed to popes who reigned during the first four centuries of the Christian era.