Around the world, men who have sex with men (MSM) face stigma and discrimination. The stigma attached to male-to-male sexual behavior hinders men from seeking appropriate health care and counseling that might reduce their risk of HIV infection and results in programs and policies that do not address the needs of MSM. Horizons approached this situation using innovative techniques for finding and interviewing MSM about their experiences in Africa and South America. While the lives of MSM in these settings are different, Horizons results highlighted HIV vulnerabilities across all the studies. The Population Council and its Horizons Program researchers were among the first to document and characterize the population of MSM in Africa, a crucial first step in developing appropriate programs for them. Findings suggested increasing outreach via peer educators and sensitizing service providers and counselors to the specific medical and prevention needs of MSM.