understanding of the underlying social and cultural dynamics of the epidemic in particular settings. Such understanding is critical to devising more effective ways of intervening to curtail the epidemic in its manifold expressions in this country and abroad. The rich array of methods includes participant observation, interviews, life histories and narratives, systematic population-based surveys, demographic and social histories of communities, demographic models of age and gender, the mapping of kin and other social networks, and the eliciting of local knowledge and taxonomies on certain topics. It also involves the study of language, which people use to convey identity and worldview and attempt to influence others. Through language, individuals are themselves influenced to behave in particular ways. Read together, one approach informs the others. Ethnographic observational studies, for example, can provide a check on the reliability of other kinds of data, such as self-reports. (As an example, see the case study on commercial sex workers in Thailand described in Part II of this report.)

Psychological, social psychological, microsociological, and microeconomic approaches are useful for focusing on the more microlevel analysis of individual behavior, partnerships, and small group interaction. They provide methods for studying social exchanges among persons and among groups; the unequal distribution of social resources; negotiation and bargaining processes, and strategic action; choice, and decision processes. All of them afford insights into key aspects of sexual and/or drug transactions that are often pursued by persons who differ greatly in their goals, relative resources, and power to affect the content and character of the exchange. All of these variables have important implications for the distribution of the behaviors that put people at risk for infection.