San Bernardino field interviews were purposely restricted to intravenous drug users (IDUs), since these were assumed to be most at risk for HIV infection. Interview subjects in Tijuana, Ciudad Juarez, Ciudad Victoria, and Cuernavaca were picked randomly, with no distinction between FSWs who were IDUs and those who were not. The research protocol for both the 1988 San Bernardino interviews and 1996-99 Mexican street studies involved the use of a standardized, 48-item, interviewer-administered, hybrid questionnaire. The interviews involved 72 FSWs in San Bernardino and 102 of their counterparts in the 4 Mexican cities. The interviews focused on differences in AIDS knowledge, fear of AIDS, health, sex, criminal histories, and injected drug use practices. The introduction to this book reviews the theoretical context, research questions, and the relationship between AIDS, intravenous drug use, and sex work. The second chapter traces the spread of HIV through drug injection and prostitution. It summarizes the incidence, prevalence, and modes of infection in reported AIDS cases among United States and Mexican FSWs. Chapter 3 presents a short history of heroin, prostitution, and their relationship, followed by a chapter that describes the Mexican study setting, methods, and subjects. Chapter 5 presents and analyzes the comparative findings from the two groups of FSWs. The sixth chapter suggests policy changes to reduce AIDS and other sexually transmitted diseases among Mexican and American prostitutes and proposes directions for the future. Differences in the health and practices of Prostitutes in Mexico and the United States are attributed to the licensing process for legal prostitutes in Mexico; the medical testing that Mexico requires prostitutes to undergo; the differences in what Mexican and U.S. prostitutes know about HIV transmission; and the difference in condom use between Mexican and U.S. prostitutes. Also discussed are the potential benefits of reforming prostitution/drug laws in both countries; the benefits of making methadone maintenance, as well as heroin and syringes, free for addicted prostitutes; and how the social support system in the United States leads to a greater proportion of drug-addicted prostitutes than are found in Mexico. Chapter tables, 266 tables, and appended interview questionnaire