Physical activity is a priority health behavior in the Healthy Campus 2010 Campaign. Promoting exercise in college students may also counter the decrease in physical activity after graduation. However, few intentional studies of college students have measured exercise habits in longitudinal studies or examined the effects of theoretically based mediators, and few theories have been empirically tested in this population. The measurement and application of behavior change theories is illustrated in this paper using the Transtheoretical Model with a sample of college students. Partial support for this model was found, particularly application of exercise stage. Basing studies on established theory is critical, but unique aspects of the population, setting, environment, and exercise mode must also be considered in exercise adherence research with college students.