An initial 2-week screening process will involve participants providing urine samples and completing physical and psychological assessments. If deemed eligible for the remainder of this double-blind study, participants will be randomly assigned to receive either bupropion or placebo over the course of 12 weeks. Participants in both the bupropion and placebo groups will receive contingency management and cognitive behavioral counseling. Participants will report to one of two clinical research sites three times per week. At each visit, participants will be examined by the study staff, provide a urine sample, and receive individual cognitive behavioral counseling sessions. At the end of 12 weeks, treatment will be stopped. Participants will return to the study site 30 days later for evaluation and to be assessed for any possible lingering side effects.