Preparing for the Drug-Free Years (PDFY) is a curriculum designed to help parents learn skills to consistently communicate clear norms against adolescent substance use, effectively and proactively manage their families, reduce family conflict, and help their children learn skills to resist antisocial peer influences. This study examined the effects of PDFY on the trajectories of these factors, as well as on the trajectory of alcohol use from early to mid adolescence. The sample consisted of 424 rural families of sixth graders from schools randomly assigned to an intervention or a control condition. Data were collected from both parents and students at pretest, posttest, and 1-, 2- and 3 1/2-year follow-ups. Latent growth models were examined. PDFY significantly reduced the growth of alcohol use and improved parent norms regarding adolescent alcohol use over time. Implications for prevention and evaluation are discussed.