Pierre de Cros, chamberlain to Pope Gregory XI from 1371 to 1378, was responsible for most of the accumulated worldly wealth of the Roman Church and for much of its activity not related to its religious character. For the purposes of political, economic, and social history, therefore, his official correspondence is of great interest. Fortunately, many of his letters were registered in the offices of the Camera Apostolica at Avignon before being dispatched, and those letters constitute the subject matter and most of the content of this book and accompanying CD-ROM.