The thesis is based on fieldwork carried out in the Tzeltal community of Tenejapa. It is concerned primarily with the practices of the "traditional" religion, which is part of a so-called cargo system. The practices are that aspect of the lives of the traditionalists that they conceive of as being the most unchanging in an environment that is otherwise altering rather rapidly. All that is considered to be part of the habitus of tradition and in particular their religion tends to be classified by the term "stalel" and to have a particular ethos. Since the Spanish Conquest, the Indians have used the practices largely unconsciously as protective mechanisms to shield themselves from mestizoisation, although they have always been and are still dependent on the Mestizos for their ceremonial prerequisites. The thesis outlines the organization of persons and the fiestas and other events that they celebrate. It discusses the substances that they use for ritual and the ceremonial language of prayer. It then looks at the people in the community who involve themselves in the cargo practices and who, by so doing, perpetuate the ethos of "stalel", year after year. Recently, however, the Indians have felt themselves to be under increasing pressure to change, an awareness that is explored during .Carnival. As various kinds of national institutional infrastructure have been provided for them in the community, they have become aware that their identity can have a positive aspect. While the numbers of those participating in the religious cargos has fallen, many have converted to various Protestant sects. Such conversions indicate a shift from an unconscious perpetuation of a particular ethos to a greater awareness of identity, and represent for the Indians a means of raising their status in their own eyes and those of the Mestizos, whilst retaining their cultural identity, which they are in the process of redefining.