Intervention;The psychological determinants of physical activity (PA) among college students may vary by ethnicity and gender, but few studies have considered these characteristics. This study tested constructs from Social Cognitive Theory (SCT) by ethnicity and gender to explain differences in PA. A total of 231 Blacks (70% female) and 218 White college students (28% female) completed the SCT questionnaire and a PA assessment two months later. Sequential regressions with interactions were used to examine how SCT constructs were associated with ethnic and gender when predicting PA. The results indicated that self-efficacy and self-regulation were significant predictors of PA for both ethnic groups and both genders. In addition, PA was statistically moderated by gender, but not by ethnicity, for perceptions of available PA facilities, with a stronger association for females. This study suggests that SCT may aid in understanding collegiate PA and help explain differences in PA between genders. Last, because of strong associations between self-efficacy and PA shown in this study, self-efficacy should be considered when developing ethnic-specific PA interventions in college students. (Contains 4 tables.)