Peter of Celle, abbot of the great Benedictine houses of Montier-la-Celle (c.1145-62) and Saint-Remi, Reims (1162-81), and bishop of Chartres (1181-3), was a figure of considerable authority and influence in twelfth-century France. Close to the royal family and to the court of Champagne, afriend of John of Salisbury and a supporter of Thomas Becket, known to Saint Bernard and to Peter the Venerable, his connections were impressive. In his letters, however, it is the concerns and ideals of the monastic world which are to the fore. At a time of unprecedented upheaval in westernreligious life, Peter's circle embraced many members of the new orders, Cistercians, Carthusians, and Grandmontines among them. His letters form an eloquent testimony to the power of friendship and co-operation at a time of frequent tension and rivalry. They offer a unique insight into the idealsand values of the monastic world, through the strong voice and critical eye of one of its leading proponents, at a crucial turning point for western religion.