This is a study of the relationships between gender, housing status, drug use, mental illness and health service utilization, as well as their impact on health status in a population of HIV-infected marginally housed individuals. The specific aims of the study are as follows: 1) To examine health service utilization (i.e., primary care, drug treatment, and mental health services) in a cohort of HIV-infected homeless and marginally individuals, and to determine differences in the patterns of health service utilization between women and men at baseline as well as over a 28 month follow-up period; 2) To examine health outcomes (physical and mental) in a cohort of HIV-infected homeless and marginally housed individuals, and to determine the extent to which women experience differences in health outcomes from men at baseline as well as over a 28 month follow-up period; and 3) To determine predisposing, enabling, and need factors influencing the differences that HIV-infected homeless and marginally housed women experience in health service utilization and health status. To achieve these specific aims, the following activities will be accomplished: 1) recruit an additional 50 women into a preexisting cohort in order to increase statistical power for gender comparisons; (2) add detailed drug use, health, victimization, subsistence needs, and health service utilization variables to the existing REACH questionnaire; (3) implement a new SCID diagnostic assessment to thoroughly assess mental health; (4) employ the use of electronic health service databases to conduct new validity studies; and (5) conduct analyses specific to these new areas of interest. Achieving the proposed specific aims will only be possible with the addition of these new activities that will ultimately yield a new class of analyses. A detailed study of the impact and interactions of gender, drug use, mental illness, health service use, competing needs like access to food, and health status will lead to a better understanding of ongoing mortality among HIV-infected marginally housed individuals and create the foundation for more effective health interventions in a variety of settings.