During the eleventh century, Christianity was accepted as the public religion in most of Scandinavia. The conversion of the Finns, a process that was not completed until the high Middle Ages, was closely related to their incorporation in the Swedish kingdom. The missionaries working in Scandinavia from the ninth century were in large part Benedictine monks. The first Nordic religious houses were a couple of Benedictine monasteries established in Denmark towards the end of the eleventh century. The ecclesiastical demands for immunities and rights of various kinds culminated in the second half of the thirteenth century. To a large extent these demands were met, but there were soon counter-reactions because the secular aristocracy and the monarchy felt threatened by the economic resources and autonomy of the Church. The doctrines and moral code of the Church influenced people's lives throughout the Middle Ages. The chapter also discusses the extent to which the teaching of the Church managed to change Scandinavian mentality.