Since the 1950's, the studies dealing with swidden agriculture or its society have developed in various disciplines including geography, cultural anthropology, agronomy, forest ecology and soil science. Though the themes handled are varied, their approaches can roughly be classified as follows: (1) an ecological approach focused on environmental change or carrying capacity, (2) a socio-economic approach focused on analysis of subsistence economy and social structure, (3) an approach from the viewpoint of ethno-science, which aims to analyze folk knowledge systems or their cosmology, and (4) a comparative approach associated with a genealogical perspective.On the other hand, there has been literature which investigates tropical swidden agricultural systems in comparison with other agricultural systems (for example, intensive irrigation agriculture). Geertz (1963) explained the difference between Inner and Outer Indonesia from their contrastive subsistence economies based on environmental factors. Taking notice of the difference of labor productivity and land productivity, Dove (1985) has developed this idea: based on the quantitative data of Indonesian agriculture, he has proposed that the swidden agricultural system has an advantage over the intensive rice irrigation system in terms of labor productivity, although the former may be inferior to the latter in land productivity. This implies that, in low population density areas, it may be rational to choose the swidden agriculture instead of intensive agriculture which the central government has recommended. His argument is considered to be important because it may offer a solution to the problem of underdeveloping countries' rural development plans propelled by the central governments and international aid organs for sustainable use.Keeping such a viewpoint in mind, I intend to discuss the economic rationality of swidden agricultural people in Southwest Ethiopia where an ethnic group (the Majangir) maintains a relatively self-sufficient subsistence economy and might be put into a critical situation by political interaction with the central government in the near future. They are living in the dense forest of the southwestern escarpment of the Ethiopian Plateau, engaging in swidden agriculture and honey collecting activity. Crops are produced for self-consumption, while they sell honey in the local market for cash. Their traditional settlements are very small: a settlement consists of only several domestic groups. They move their houses according to abandonment of their swidden fields every few years. Since the Ethiopian socialist revolution in 1974, however, sedentarization has been encouraged by the central government. At almost the same time, Christianity was introduced to them by a Protestant missionary. Sedentarization and Christianity have had a great impact on the society.From December 1992 through March 1994, I stayed in a village called Kumi which contains about 470 people. In this village, sedentarization and introduction of Christianity influenced them from a relatively early time. During my stay I made participant observations of their everyday life including agricultural practices, and I especially paid attention to the quantitative aspect of labor input and its seasonal allocation.I observed technological features of their farming system which can be summarized as follows:(1) Diversity of field types: I classified field types into five: (a) main fields cleared in the dry season (b) main fields cleared in the rainy season (c) sweet potato fields (d) fruit garden (e) backyard garden. Among them, worthy of note is (b) type, kate fields. Majangir adopts a peculiar way of farming, in which they first sow maize and sorghum directly in the bush, and then clear the grasses and shrubs. They cover the ground with them instead of burning. This farming technique allow them to prepare main fields at the height of the rainy season.