The demographics of the human immunodeficiency virus (HIV) epidemic have changed from impacting affluent white gay men to impacting the poor, people of color, the young, and women. Sexually transmitted diseases (STDs) disproportionately affect these same populations. One approach that stresses the inclusion of the voices of marginalized individuals--participatory learning and action (PLA)--offers an opportunity to make HIV prevention a more innovative, effective, and collaborative effort. The key to PLA is participation by local people, often in groups, in the investigation of a problem. Their participation might include open-ended sharing and analysis, which often involves visual methods such as diagraming and mapping the community environment. The second basic component is questioning the behavior and attitudes of outsiders, who are urged to listen to, learn from, and respect local people. The third component is the encouragement of creativity and flexibility over formality and codification of the techniques. Extensive use of PLA in rural areas of the global South has shown that the method generates valid and reliable quantitative and qualitative data. Advantages of the method include its ability to access members of "hidden" populations that cannot be reached by conventional survey research and the empowerment of local people. Six visual techniques used in PLA are discussed. (Contains 19 references.) (TD)