In this study, 200 nicotine-dependent cigarette smokers will participate in an 8-week, double-blind, placebo-controlled trial and then will be followed over 4 years. Participants will be randomly assigned to receive either selegiline or placebo. Selegiline doses of 5 mg will be taken once a day during the first week. This will be increased to 5 mg twice daily for the remaining 7 weeks. The target smoking "quit date" will be Day 15. All smokers will receive brief weekly manualized smoking cessation counseling from the Mayo Clinic's "Smoke Free and Livin' It" program. The primary smoking cessation outcome measure will be 7-day point prevalence smoking abstinence at the 6-month follow-up. Secondary cessation outcome measures will include continuous smoking abstinence during the last four weeks of the trial (Days 29-56) and 7-day point prevalence abstinence at the end of the 8-week trial (Days 49-56).