Background: Evidence suggests that health promotion interventions that are based on behavioral theories are more effective than those lacking a theoretical base. Recent studies have begun to look at the relationship between social cognitive variables and physical activity in varied populations. Purpose: The purpose of this study is to determine the association of the Social Cognitive Theory (SCT) constructs in predicting 4 weeks of discretionary leisure time physical activity among Appalachian high school students. Methods: A prospective design was used to measure physical activity over 4 weeks following the measurement of the social cognitive theory variables. Linear regression was used to describe the association between the variables and 4 weeks of physical activity. Results: Together the SCT constructs accounted for 24% of the variance in moderate physical activity and 38.6% of the variance in vigorous physical activity. Discussion: The results of this study demonstrate that SCT variables are determinants of physical activity for this sample. The regression models for moderate and vigorous activity accounted for significant portions of variance and retained all 4 SCT variables in each model. Translation to Health Education Practice: This study contributes to the identification of targets for intervention for practitioners who work with Appalachian high school students.