In this study, researchers from UCLA and Friends Community Center will work together in designing a program to assist young homeless stimulant-using gay and bisexual homeless men to complete the hepatitis vaccine and in reducing drug and sexual activity. Using nurse case management strategies, found successful with homeless adults as well as contingency management strategies, found successful with gay and bisexual homeless adults by the community partners, the investigators will evaluate the effectiveness of a program that combines both strategies. As stimulant use threatens to increase homeless persons' risk of exposure to hepatitis A and B viruses, particularly among young users who may not yet be HBV-infected, this research is targeted to engage this group in treatment, until they are suitably protected from HBV, and hopefully reduce risk for HCV and HIV as well.