 This study is a prospective, open cohort study of smokers who undergo a smoking cessation program, and who subsequently may or may not resume smoking spontaneously. Eligible subjects will be characterized at baseline with respect to their metabolic and CVD risk profiles, body fat composition and distribution. Subjects will then undergo an intensive 8-week smoking cessation program using bupropion plus cognitive behavioral counseling. Those who successfully abstain will be reassessed. Since most individuals who quit smoking will naturally resume smoking again over time, subjects will be assessed again after an additional 4 months of follow-up when a subset of subjects will be expected to have naturally resumed smoking. 