Anthropologists have long been interested in the diversity of man's food-getting activties, having attempted various classifications of human groups based on the nature of the activity. The most classic and popular example may be the classification of societies into such general types as follows (FIRTH, 1953) I Food-gatherers, hunters, and fishers. II Pastoralists. III Agriculturalists. IV Artisans. Another example is the classification of primitive economies into such major types as follows (JACOBS and STERN, 1948) I. Hunting, fishing, food-gathering economies a . that lacked exchangeable surpluses. These will be designated as simple food-gathering economies. b . that produced small exchangeable surpluses. These will be referred to as advanced food-gathering economies. II. Economies based on primitive agriculture, or on pastoralism, or on primitive agriculture and pastoralism a . that lacked pastoralism and produced small surpluses. These will be referred to as simple agricultural economies. b . with or without pastoralism and that produced large surpluses. These will be referred to as advanced agricultural or agricultural-pastoral economies. These classifications all were based on the ways of food-getting or the patterns of food-economies. In short, these were the classifications of food-getting activities from the economic point of view. Traditional anthropological-ethnological studies lacked perspectives on the diversity of human food habit. Animals are classified according to the food habit or dietary habit into such major types as herbivores, carnivores, and omnivores. Man's food habit also varies greatly. Moreover, it is one of the fundamental problems on hominization and human evolution. From this point of view, a systematic study of man's food habit may be necessary. Ethnographic reports show that there is a wide variation in food habits among hunter-gatherers ; however, there has been no systematic study of it. My point is to discuss a possibility of systematically studying the diversity of hunter-gatherers' food habits on the basis of available ethnographic data. What will be attempted here is the classification on their food habits from an ecological-evolutionary point of view. It means that the criteria for the classfication are selected from among those which are significant from an ecological or evolutionary point of view. The most important and fundamental criterion adopted here is the staple food or principal element of the diet of a given people. The second major criterion is the relative size of animals which are hunted. The reason for this is that a distinction between small animals and larger animals is necessary if we are to discuss hunter-gatherers' food habits from the view point of hominization. The third essential criterion of this classification system is a distinction between land animals and aquatic animals as the principal food of a given people, which is significant from the view point of the dispersal of man and the evolution of human food habit. Through the criteria of food habits, modern hunter-gatherers can be classified into three major types and four subtypes as indicated in Figs. 3 and 4. Among hunter-gatherers, there are two extreme types. One is characterized by a strong vegetarian habit and is designated here as the vegetarians or plant-eaters (Type I) . An important subsidiary criterion of this group is underdeveloped hunting characterized by adult males as part-time hunters.