Based upon advice from our community partners who have successfully treated SA-using gay and bisexual men (GBM), we will incorporate contingency management into our vaccination completion program, which had lower completion rates among young adults and MSMs. Thus, in this competitive renewal, we propose a randomized, experimental, two-group design to evaluate the effectiveness of a Nurse Case Managed Program, which includes specialized education and Contingency Management and Tracking (NCCMT), with a Standard Program, including brief education, Contingency Management and Tracking (SCMT) with 500 homeless, young (18-39), SA-using GBM, on completion of the Twinrix HAV/HBV vaccine and, secondarily, on reduction of risk for hepatitis and HIV. This study is innovative in that it will allow us to look at the effect of an enhanced case management and contingency management program versus a standard contingency management program. The proposed study combines optimal strategies to approach, engage and intervene with a hidden and high-risk population to assess the feasibility and efficacy of interventions that may prove beneficial in preventing HBV and HAV infections. We will also assess the relative cost of these programs in terms of completion of the HAV/HBV vaccination series. As use of SAs threatens to intensify homeless persons' risk of exposure to HAV and HBV, particularly among young users who may not yet be HBV-infected, research targeted to engage this group in treatment, until they are suitably protected from HBV, is critical.