Injection drug use has significant health consequences, including high rates of HIV and hepatitis C transmission. These problems have been exacerbated in recent years by the use of crystal methamphetamine (commonly called crystal meth), particularly in BC. Methamphetamine use is becoming increasingly common among marginalized youth, particularly those whose social and economic environment is the street. It is estimated there are between 45,000 to 150,000 street-involved youth in Canada, most of whom live in the large urban centres of Toronto, Montreal and Vancouver. Illicit drug use and unsafe sexual practices, including unprotected sex and sex trade work, increase susceptibility to HIV infection among street-involved youth. Brandon Marshall is one of the few researchers investigating the relationship between illicit drug use and sexual risk behaviours among street-involved youth. Using data collected from the B.C. Centre for Excellence in HIV/AIDS At-Risk Youth Study, he will examine how different social, structural, and environmental factors impact sexual practices. Specific factors include the age of first sexual experience, sexual orientation, illicit drug use, sexual relationships with older partners, access to health services, and involvement in the Downtown Eastside community of Vancouver, where drug use and poverty are prominent. This research will improve our understanding of illicit drug use and sexual activity in marginalized youth and will play an important role in developing sexual health education and prevention programs for youth at-risk.