The first chapter presents a wide-ranging account of the long history of heroin addiction in the United States, along with the development of pertinent legislation. Another chapter describes the characteristics of a large population of heroin users who were interviewed as part of a project that assessed the effectiveness of AIDS prevention messages to "street" populations of intravenous drug users. Findings show that many heroin users survive for long periods of time and continue their use. A third chapter focuses on the cyclic re-emergence of increasing numbers of new heroin users and how these numbers can be and have been exacerbated by the prevalence of crack/cocaine users. Another chapter reports on recent developments in the heroin histories of a probability sample of African Americans residing in households in the Central Harlem Health District of New York City. One chapter reports on an analysis that targeted the extent to which heroin use increased from 1987 to 1993 in a high-risk subpopulation (i.e., arrestees booked for criminal offenses). The sixth chapter analyzes the determinants and health risks associated with noninjecting heroin users who convert or do not convert to injection use. This is followed by a chapter that traces the changes and social perceptions of what has been called the most controversial intervention for heroin addiction; methadone maintenance treatment for heroin addiction is traced over a 30-year period to determine its effectiveness. Chapter 8 reports the qualitative results of a longitudinal study that assessed clients' perceptions of methadone maintenance programs and how the changes in funding are impacting these programs. The final chapter discusses the changes in the world heroin market that may signal changes in the routes of administration of heroin. Chapter references and a subject index