Objective: There is a dearth of studies on the mechanisms of multiple risk behaviors, even though these behaviors are significant public health issues. The authors investigated whether health behavior interventions have transfer or compensatory effects on other health behaviors. Participants and Methods: The authors looked at transfer and compensation effects of 3 health behaviors (smoking, alcohol use, and physical activity) in a sample of college students aged 18 to 25 years (N = 973; 84% born in the United States; 50% female; 25% Japanese, 19% Caucasian, 16% mixed). Results: The study revealed the following evidence for transfer effects: (1) nonsmokers consume less alcohol, (2) regularly active people smoke less, and (3) nondrinkers smoke less. The authors also found the following compensation effects: (1) regularly active people consume alcohol more frequently; and (2) alcohol drinkers are more active. Conclusions: Interventions involving college students' smoking, alcohol use, and physical activity need to take into account both transfer and compensation considerations to maximize health impacts. (Contains 3 tables.)