The primary purpose of this project is to assess the utility (risks and benefits) of testing and informing intravenous drug abusers of their HIV antibody serological status as an aid to reducing AIDS- related high risk behavior (primarily needle-sharing). 1. We will assess the prevalence of HIV antibody seropositivity in two populations of Baltimore drug abusers -- a methadone treated cohort (N=200), and an untreated cohort (N=200). 2. In both a methadone treated population and an untreated drug abusing population we will conduct a parallel-groups randomized trial to assess the utility of HIV antibody serological testing and feedback to patients of their serological status as an aid to enhancing changes in risk related behaviors and to assess the effect of such testing and feedback on levels of psychiatric distress. 3. In both populations we will assess the relationship between current serological status and history of risk related behaviors. 4. In both populations we will assess whether an AIDS risk reduction education program is acceptable to (attended by) drug abusers and whether it is associated with a reduced frequency of high risk behaviors compared to pre-education. 5. We will follow both populations prospectively for two years to assess changes in seropositivity, risk behaviors, and health status. This research will provide important information about the epidemiology of HIV exposure among drug abusers, and about its relationship to individual characteristics and behaviors over time and, most importantly, it will provide valuable information concerning the effects of potential intervention procedures for reducing the spread of the AIDS virus (HIV).