AIDS and drug addiction is a topic of great and growing concern. AIDS first appeared among intravenous drug users in Europe in 1984, three years after the first cases were seen among homosexuals. This epidemic has spread more rapidly among intravenous drug users than in any other risk group. The high rates of HIV-1 seroprevalence among drug users in France, Italy, and Spain account for 85% of the total number of AIDS in intravenous drug users in Europe. It is anticipated that HIV-infected drug users will soon place a heavy burden on both drug treatment facilities and specialized health care units. The HIV-1 epidemic will also cross the former iron curtain. This contribution covers the wide and complex scene of drug problems and addiction as a whole. It gives researchers an opportunity to obtain background information on the spread of HIV and AIDS among intravenous drug users as well as on the clinical and psychological effects of HIV-1 infection and AIDS in Europe. The topics reviewed include surveys of intravenous drug use, HIV prevalence, detoxification, risk reduction, changing health behaviors, evaluating AIDS interventions and the impact of methadone maintenance treatment. This monograph will be of value to all clinicians, researchers, and policy makers who are concerned with the connection between intravenous drug use and AIDS.