Little is known about how the reasons that college student drinkers and abstainers have for choosing not to drink might differ. The present study examined this issue among a sample of 2,500 U.S. college students from 18 colleges and universities. Abstainers endorsed significantly more reasons for not drinking than drinkers, and among drinkers, light drinkers endorsed more reasons than heavy drinkers. Abstainers' decision not to drink appeared to be a lifestyle choice that was supported by multiple reasons, including personal values, religious beliefs, not wanting the image of a drinker, and beliefs about alcohol's effect on behavior. Heavy drinkers were more likely to endorse situational reasons such as having to drive home later or being concerned about school work or weight gain from drinking. Implications of these findings for alcohol prevention work on college and university campuses are discussed.