Gender beliefs affect adolescents' sexual motivations, perceptions, and actions (Moss, 1994) and can endanger sexual health (Haffner, 1998). We believe that teaching youth about gender norms will increase the efficacy of HIV/STD preventive interventions. We were funded by the National Institute of Child Health and Human Development to develop and evaluate a gender-based intervention for youth aged 13-16. In this paper we summarize the literature on how biological sex and gender roles influence sexual risk behavior among teenagers, summarize some of our own data on gender beliefs of teenagers, describe the Reel World program that we developed to teach gender, and discuss the challenges we faced in teaching gender norms to youth and how we addressed them.