AIDS has become a serious problems in prisons in the United States. Large numbers of infected inmates may be spreading HIV through widespread male homosexual contract. In contrast, the extent of AIDS infection among inmates in Mexican prisons is largely unknown. In United States prisons, policies regarding AIDS vary. The policies include mass testing and segregation of inmates with HIV infection, mandatory testing of persons at risk of AIDS, AIDS prevention education, and programs to provide condoms and information on how to sterilize needles. In Mexico, the universal policy allowing conjugal visits may reduce the risk of transmission of AIDS via male homosexual activity. Policies vary widely and include voluntary HIV antibody testing, mandatory AIDS tests, and segregation of infected inmates. Mexico may eventually experience a high rate of AIDS infection within its correctional facilities, but its experience will probably differ significantly from that of the United States by being restricted to intravenous drug users and a small homosexual population. The two countries can learn from each other in dealing with AIDS in correctional facilities. Footnotes and 40 references (Author summary modified)