In this context, the term hidden populations refers to a subset of the general populations whose members are not readily identified through existing knowledge or sampling capabilities. Sources available to answer research questions include secondary indicator data, institutional and professional authorities, and indigenous informants. Once available sampling frames and unit of analysis are evaluated, ethnographers must gain access to the target population through immersion in the social scene, developing a rapport with their subjects and legitimacy for the actual research. Two factors which seem imperative in maximizing access to hidden populations include the use of community-based field stations and the payment of subject fees. 8 references