Although young, sexually-active heterosexuals have always been at risk for contracting sexually transmitted diseases, the recent appearance of Acquired Immunodeficiency Syndrome (AIDS) has increased the possible peril of sexual experimentation. Currently, behaviors to reduce the risk of contracting AIDS are being widely advocated. The present study examines predictors of self-reported risk reduction behaviors in a sample of 188 young, sexually-active heterosexuals. Three factors (perceptions of personal vulnerability, sexual behavior history, and homophobia) were hypothesized to predict levels of worry about contracting a sexually transmitted disease. Worry, in turn, was hypothesized to predict behavior change. Structural equation modeling provided support for these predictions, but found somewhat different patterns for women and men. For both sexes, higher levels of worry were a significant predictor of risk reduction behavior implementation. For women only, more extensive sexual behavior histories significantly predicted levels of worry. In contrast, for men only, perceptions of personal vulnerability and homophobia were significant predictors of worry. Results suggest that gender plays an important role in understanding cognitive predictors of sexual risk reduction behaviors. © 1991.