Objectives: To examine the contributions of self-efficacy, outcome expectations, barriers, and demographic/health factors to physical activity behavior in primary care outpatients and to determine differences in these associations for African American versus Caucasian patients. Design: Cross-sectional, structured interview. Participants and Setting: Adult internal medicine outpatients (n=393, response rate 88.5%) were enrolled. Most were female (70%) and Caucasian (62%) with a yearly household income <$20,000 (54%) and history of arthritis (57%). Mean age was 48.9±11.8 years and BMI was 30.9±8.16 kg/m2. Measurements: A 30-minute structured interview assessed self-reported leisure-time physical activity, self-efficacy, outcome expectations, perceived barriers, and demographic/ health covariates. Results: Based on path analysis, social cognitive constructs accounted for 28% of the variance in physical activity in African American patients and 25% in Caucasian patients. After controlling for selected covariates, path analysis showed a direct association between self-efficacy and physical activity for African American (β=.45, P<.01) and Caucasian patients (β=.34, P<.01). Although higher self-efficacy was associated with higher outcome expectations for both groups (β=.25, P<.05, β=.21, P<.05, respectively), no direct association was found for outcome expectations with activity. Self-efficacy demonstrated an indirect association with activity through perceived barriers for Caucasian patients only. Conclusions: Self-efficacy and perceived barriers were the most important independent correlates of physical activity with potential racial differences warranting further study noted.