Persons with serious mental illness (SMI) are at increased risk for HIV/AIDS. The relative risk of HIV/AIDS is at least five times greater in SMI as the general Medicaid population in Philadelphia and over seven times for those also treated for substance abuse. SMI persons reported more transmissions through heterosexual contact, injection drug use (IDU), and women have more sex with men who have sex with men (MSM) than in the general population. A cost study showed that SMI with HIV had much higher health care costs than non-SMI persons with HIV and non-HIV persons with SMI. We will implement a prevention program for persons with SMI who also abuse substances. A comprehensive pilot study demonstrated convincingly that SMI participants were able to learn from case managers teaching HIV prevention skills. Preventing AIDS through Health (PATH) is a translation of two HIV prevention programs proven effective in the general population and among substance users. The RESPECT program was developed by CDC and is the first HIV prevention program to show one-on-one counseling can reduce at-risk sexual behavior in a multi-site demonstration. The NIDA Community-Based Outreach Model (CBOM) was designed to reduce the risk of HIV and other blood-borne infections in drug users. Both are highly structured, manualized interventions. PATH uses case managers (CMs) to draw on features of both interventions depending on individual consumer risk profiles. CMs have specialized expertise in providing services to this population. We believe that this expertise, prior relationships with these persons, and an ability to reinforce regularly the intervention will result in significantly reduced risk. Blood testing will identify those who are HIV positive at baseline. Breathalyzer and urine testing will supplement clinical interviews and other measures to identify substance abuse co-morbidity. Using a longitudinal experimental and control group design, we will randomly assign case managers to deliver the intervention to consenting participants in their caseloads who meet inclusion criteria. Participants will be in treatment at a large CMHC in Philadelphia. Independent interviews will be conducted with case managers and consumers before the intervention, and again at 3, 6 and 12-months post intervention and focus on changes in risk behaviors, fidelity of translation of the intervention, cost and outcomes. Breathalyzer and urine tests at 12-months will supplement self-reports of use of alcohol, cocaine, marijuana, benzodiazapines, and opiates.