Statements are frequently made by residents and travellers in Africa about the effects of missions on Native communities, but they are seldom backed by an analysis of concrete facts. The African is subject to the influences of Western European culture in many different ways, and it is extremely difficult to isolate the influence of missions from other contact influences, particularly since African Christians tend, for a variety of reasons, to be more affected by these other influences than their pagan neighbour. By comparing, in one area, the life of pagan and Christian families which are subject to similar non-Christian contact influences it is, however, possible to study specific differences in belief and behaviour. One such observable difference is found in the believed working of religious sanctions. Among the Nyakyusa of South Tanganyika behaviour in the pagan community is directly affected by the belief that certain actions are punished by the ancestors, by witchcraft, or by magic. Christian teachers attack these beliefs. The problem then arises as to how far belief in traditional religious sanctions remains in the Christian community, how far it is replaced or modified, and how far changes in belief affect behaviour.