The purpose of this study was to examine cognitive constructs from the theory of planned behavior (i.e., attitude, perceived behavioral control, and intention) as potential mediators of the relationship between selected social influence constructs (i.e., subjective norm, social support, and cohesion) and adherence to structured exercise classes. Sixty-two participants completed self-administered questionnaires during the fourth week (social influence constructs) and eighth week (cognitive constructs) of a 12-week exercise program. Exercise adherence was monitored during weeks 9 through 12 using perceived intensity and attendance. Pearson correlations indicated that social support correlated with perceived behavioral control, whereas cohesion correlated with attitude. Path analysis supported two distinct paths from social influence to exercise adherence: (a) social support-->perceived behavioral control-->intention-->exercise adherence, and (b) cohesion-->attitude-->intention-->exercise adherence. Discussion focuses on the theoretical importance of these findings, conceptual and measurement issues regarding subjective norm, and suggestions for future research.