Hierarchical regression analysis was used to test the hypothesis that specific functional factors of marijuana use would predict past 30-day marijuana use in 425 college students more precisely than demographic variables alone. This hypothesis was confirmed. Functional factors of personal/physical enhancement as well as activity enhancement were significant predictors of 30-day marijuana use. Furthermore, this model explained over half of the variance of students' monthly marijuana use. Implications for future research and practice are discussed. (Contains 3 tables.)