Hookups--casual sexual encounters that may or may not include intercourse - are common on college campuses. Previous research has suggested that these casual sexual encounters may have serious health-related consequences. Understanding the relationships among multiple predictors of hooking up is important if high-risk prevention programming among college students is to be effective. This study considers each of the Big Five personality traits as predictors of hooking-up behaviors in a sample of Midwestern undergraduates (N = 247). Fifty-six percent of women and 63% of men reported engaging in a hookup. In general, Extraversion was positively associated with hooking up behaviors; Conscientiousness was negatively associated with hooking up. Relationships between personality and hooking up were significant while controlling for alcohol use. Implications for prevention programming on college campuses are discussed.