Inclusion Criteria:

1. are between 18 and 65 years of age
2. are current smokers (i.e., smoking at least 10 cigarettes per day)
3. are sedentary, i.e., have not participated regularly in aerobic physical exercise (for at least 20 minutes per day, 3 days per week) for the past six months.

Exclusion Criteria:

1. current DSM-IV Axis I psychiatric disorder as assessed by SCID-NP
2. Substance abuse or dependence (excluding nicotine dependence) within the past 6 months
3. lifetime DSM-IV diagnosis of a bipolar disorder as assessed by the SCID-NP
4. lifetime history of a psychotic disorder or current psychotic symptoms as assessed by the SCID-NP
5. current suicidality or homicidality
6. marked organic impairment
7. physical disabilities or medical problems (such as a history of diabetes, hypertension, seizure disorder, coronary heart disease, valvular heart disease, and pulmonary disease) or use of medications (such as beta blockers) that would prevent or hinder participation in a program of moderate intensity exercise
8. current pregnancy of intent to become pregnant during the next 12 weeks, and i) current use of any pharmacotherapy, including transdermal nicotine replacement, for smoking cessation