The overall goal of this research is to increase our understanding of the role of individual genetic differences in response to bupropion treatment and the psychobiological mechanisms by which genetic and treatment factors interact in the smoking cessation process. The ultimate objective is to provide information necessary to match bupropion vs. behavioral counseling cessation treatment to those smokers with the greatest need and likelihood of benefit. This study is a double-blind randomized placebo-controlled clinical trial of bupropion HCL (brand name Zyban) in adult male and female smokers. The factorial design includes one treatment factor (bupropion 300 mg/day + counseling vs. placebo + counseling) and several subject factors (e.g. genotype, personality). Smoking history, psychological status will be assessed at baseline and blood will be drawn for genotyping. Bupropion or placebo will be delivered over a 10-week treatment period and subjects will be instructed to quit smoking after two weeks of medication (week 3 of treatment). All subjects will also receive a 7-week group behavioral smoking cessation treatment (over an 11 week period). This study may yield information that will help clinicians identify the most effective smoking cessation treatment for a particular patient, based on his/her background.

Inclusion Criteria:

Eligible smokers will be those currently smoking at least 10 cigarettes a day.

Exclusion Criteria:

Exclusionary criteria are: planning a pregnancy, pregnancy, lactating, seizure disorder, history of head trauma or prior seizure, family history of a seizure disorder, brain (or CNS) tumor, history of or currently diagnosed with bulimia or anorexia nervosa, diabetes treated with oral hypoglycemics or insulin, excessive use of alcohol or alcoholism, current addiction to opiates, cocaine, or stimulants, use of other drugs containing bupropion (e.g., Wellbutrin, Wellbutrin SR), allergy to bupropion, currently taking particular medications (e.g., monoamine oxidase inhibitor, antipsychotics, antidepressants, theophylline, systemic steroids, over-the-counter stimulants and anorectics), recently taken a MAOI (less than 14 days) or a recent discontinuation of a benzodiazepine.