PURPOSEThis study evaluated the theory of planned behavior (TPB) as a framework for understanding exercise adherence during phase II cardiac rehabilitation (CR).METHODSA total of 215 patients completed a baseline questionnaire that included the TPB constructs and past exercise. Exercise adherence was measured via program attendance during phase II CR.RESULTSHierarchic regression analyses indicated that attitude, subjective norm, and perceived behavioral control (PBC) explained 30% of the variance in exercise intention, with attitude, subjective norm, and PBC each making significant unique contributions to intention. Furthermore, exercise intention explained 12% of the variance in exercise adherence. Finally, the behavioral, normative, and control beliefs provided novel information concerning why patients in phase II CR hold certain attitudes, subjective norms, PBC, and exercise intentions.CONCLUSIONResults of the present study provide evidence that the TPB is a useful framework for understanding exercise intentions and adherence during phase II CR.