Pstudy investigated the effects of baseline levels of academic achievement and longitudinal trends in normative beliefs on adolescent substance initiation across a 42-month time period. Participants were 272 rural adolescents who were an average of 12.3 years old at the baseline assessment. Academic achievement positively predicted the intercept and negatively predicted the growth-trajectory of normative beliefs regarding peer substance behavior. Further, baseline academic achievement negatively predicted initial levels, as well as the growth-trajectory, of substance initiation. The discussion addresses the influence of academic achievement and normative beliefs on substance initiation and the utility of latent growth curve modeling in studying longitudinal change. In addition, implications for prevention programming are discussed. (Contains 1 author note and 1 footnote.)