There exists a well-established relationship between smoking and depressive symptomatology. The problem of relapse continues to plague public health efforts to reduce the prevalence of cigarette smoking among smokers with elevated depressive symptoms. Intervening to increase aerobic exercise among smokers with elevated depressive symptoms represents one potentially efficacious approach for it may directly influence cessation outcomes and have ancillary physical and mental health benefits in this population. In a small pilot trial (K23 DA019950; PI Ana Abrantes, PhD), we demonstrated that the subgroup of smokers with elevated depressive symptoms who participated in the exercise condition (relative to the health education contact control) had higher abstinence rates at end of treatment and up to the 12-month follow-up. In addition, participants in the exercise condition also demonstrated significantly lower negative affect related withdrawal symptoms as well as depressive symptoms in the early weeks of smoking cessation. This preliminary work is the first study to demonstrate that an at-risk group of smokers with elevated depressive symptoms could uniquely benefit from exercise while quitting smoking. We propose to conduct a randomized, controlled trial with 250 smokers with currently elevated depressive symptoms to test the efficacy of a 12-week, moderate-intensity aerobic exercise intervention (AE) vs. a 12- session, health education comparison (HEC) condition. Both conditions will be equated for therapist and participant contact time. Participants in both conditions will receive identical smoking cessation sessions - 8 weeks of telephone counseling with transdermal nicotine patch (TNP). While capitalizing on the synergistic effects of exercise for both reducing depressive symptoms and promoting smoking cessation, the long-term goal of this program of research is to develop an effective, disseminable exercise intervention that can aid smokers with elevated depressive symptoms quit smoking. We expect that the results of this study will establish the AE intervention as efficacious for tobacco cessation in smokers with elevated depressive symptoms and will produce valuable scientific knowledge regarding the psychological and biological mechanisms of action. The public health significance of this program of research lies in the potential for adapting the AE intervention for future dissemination to community fitness venues (e.g., YMCA, local health club/gym), primary care settings and for use in conjunction with state tobacco quitlines, in the hopes of decreasing the overall prevalence of cigarette smoking, thereby reducing smoking-related morbidity and mortality.