In this paper I theorize that low self-control is a reason why offenders are at high risk of being victims of crime. I reformulate self-control theory into a theory of vulnerability and test several of its hypotheses, using data from a survey administered to a sample of college students. This research investigates how well self-control explains different forms of victimization, and the extent to which self-control mediates the effects of gender and family income on victimization. Low self-control significantly increases the odds of both personal and property victimization and substantially reduces the effects of gender and income. When criminal behavior is controlled, the self-control measure still has a significant direct effect on victimization. These results have many implications for victimization research.