In this article we argue that the concept of knowledge, as utilized by public health professionals, is best regarded as cultural belief, as defined in anthropology. The implications of this position are explored, particularly as it relates to the development of a decision-making approach to the understanding and analysis of health care behavior. The methodological challenges posed by the new theoretical perspective that has emerged from the emphasis on decision making is discussed from the perspective of applied research. The role of focused ethnographic studies is examined and contrasted with ethnomedicine and survey approaches. Some main features of focused ethnographic methods are described and illustrated with a case example of acute respiratory infection (ARI) in Gambia.