The purpose of this study is to identify the prevalence of and risk factors for HTLV-III/LAV infection among entrants into prison, and more specifically, for parenteral drug users (PDUs) within this group. Cases of Acquired Immunodeficiency Syndrome (AIDS) have been reported within prisons, and inmate populations include sizeable numbers of persons at high risk for HTLV-III/LAV infection. This study will provide information to assess the relative importance of established risk factors at time of entry into prison; this information has implications both for refinement of educational interventions to inmates and for assisting correctional medical personnel to identify efficiently those who may benefit from additional medical evaluation. Also, access to PDUs within the community is limited. Drug abuse treatment centers receive a fraction of total PDUs who are usually self-selected; up to 80% of these individuals have a prior history of incarceration. In contrast, only 13-50% of PDUs at entry into prison have a prior history of treatment. Therefore, with detailed interviews of PDUs at time of entry into prison, use-related risk factors within a wider segment of the community can be determined. This information has implications for refinement of educational interventions to PDUs both within and outside prison. We propose to conduct a seroprevalence survey among 5,000 incoming inmates to the Maryland State Prison System during a twelve month period, followed by case-control studies of variables associated with (or predictive of) seropositivity to HTLV-III/LAV. This study will enroll male subjects at the Reception and Diagnostic Classification Center (RDCC) and female subjects at the Maryland Correctional Institute for Women (MCI-W), the points of entry for all inmates. Sero collected routinely from all inmates will be tested for HTLV-III/LAV antibody. All inmate records will be abstracted for information routinely collected by intake personnel. A trained interviewer will conduct a special study interview with eligible and consenting inmates to elicit information on established risk factors for HTLV-III/LAV infection and, for PDUs, use-related activities that may increase risk for infection within these subgroups (e.g., type of drugs, frequency, social networks, individual practices, etc.). For the case-control studies, risk factor information on cases (seropositives) and controls (seronegatives) will be compared using univariate and multivariate techniques. The Maryland Prison population is 96% male, 76% Black, and 80% ages 18-35; demographic criminal offense and sentence categories have remained stable for several years. Based upon preliminary studies, over 350 seropositive inmates, approximately 225 of which are PDUs, will be eligible as cases for the analyses proposed.