This study examined differences in predictors of marijuana use versus quantity of marijuana use across the high school years, using annual assessments from the Oregon Youth Study (OYS) and a two-part model for semicontinuous data. The OYS is a community sample of at-risk boys followed from age 10 years. In order to capture dynamic prediction effects, change scores of predictors across the high school years were included, as well as baseline scores. As hypothesized, baseline predictors predominantly showed associations with the intercepts but not with the slopes of marijuana use and quantity of use. Changes in parental monitoring, peer substance use, and antisocial behavior and deviant associations were associated with growth in marijuana use and quantity of use. Findings highlight the differential associations individual and contextual risk and protective factors have with both initial levels and growth in boys’ marijuana use compared with quantity of use across the high school years.