Prepartying, also known as pre-gaming, has emerged as a high-risk drinking event among U.S. college students. Research on factors related to prepartying behavior is in its relative infancy. The present study provides prevalence rates for prepartying across ethnic groups and examines how social context (whether prepartying took place with primarily male, female, or coed groups) and demographic factors may influence prepartying behavior. Participants were students from two West Coast universities (N = 2,546) whom identified as White, Asian and Pacific Islander American (APIA), Hispanic/Latino(a), or African American. The percentage of students who reported prepartying at least once in the past month, as well as the frequency and number of drinks consumed for prepartying occasions, varied by ethnic group and sex. A greater proportion of White students (60%) reported prepartying than Hispanic/Latino(a) (52%), African American (44%), and APIA (37%) students, though Hispanic/Latino(a) students who prepartied did so as often and consumed similar amounts of alcohol as White prepartiers. Across all ethnic groups, females who reported prepartying in coed groups consumed significantly more drinks than those who prepartied in primarily female groups. Finally, prepartiers within all ethnic groups consumed more drinks per week and experienced a higher number of alcohol-related consequences than non-prepartiers. The results suggest that future research and prevention programs should target prepartying and other high-risk events in at-risk students of ethnically diverse backgrounds and also consider the effects of gender in prepartying contexts on alcohol use