OUTLINE: This is a randomized, double-blind, placebo-controlled, multicenter study. Patients are stratified according to gender, cigarettes smoked per day at time of screening (10-39 vs 40 or more), and total length of smoking in years (less than 5 vs 5-9 vs 10 or more). Participants are randomized to one of three treatment arms. Arm I: Participants receive 6-16 nicotine inhaler cartridges per day. Arm II: Participants receive oral bupropion 1-2 times daily. Arm III: Participants receive 6-16 nicotine inhaler cartridges per day and oral bupropion 1-2 times daily. In all arms, treatment continues for 12 weeks. After 12 weeks, participants are randomized a second time based on whether they continue to smoke or are smoke-free. Participants randomized to arm I who continue to smoke are randomized to one of two treatment arms. Arm IV: Participants receive oral bupropion 1-2 times daily for 12 weeks Arm V: Participants receive oral placebo 1-2 times daily for 12 weeks. Participants randomized to arm II who continue to smoke are randomized to one of two treatment arms. Arm VI: Participants receive 6-16 nicotine inhaler cartridges per day for 12 weeks. Arm VII: Participants receive 6-16 placebo inhaler cartridges per day for 12 weeks. Participants randomized to arm III who continue to smoke do not receive any further therapy. Participants randomized to arm I who are smoke-free are randomized to one of two treatment arms. Arm VIII: Participants receive 6-16 nicotine inhaler cartridges per day for 40 weeks. Arm IX: Participants receive 6-16 placebo inhaler cartridges per day for 40 weeks. Participants randomized to arm II who are smoke-free are randomized to one of two treatment arms. Arm X: Participants receive oral bupropion 1-2 times daily for 40 weeks. Arm XI: Participants receive oral placebo 1-2 times daily for 40 weeks. Participants randomized to arm III who are smoke-free are randomized to one of four treatment arms. Arm XII: Participants receive 6-16 nicotine inhaler cartridges per day and oral placebo 1-2 times daily for 40 weeks. Arm XIII: Participants receive 6-16 placebo inhaler cartridges per day and oral bupropion 1-2 times daily for 40 weeks. Arm XIV: Participants receive 6-16 nicotine inhaler cartridges per day and oral bupropion 1-2 times daily for 40 weeks. Arm XV: Participants receive 6-16 placebo inhaler cartridges per day and oral placebo 1-2 times daily for 40 weeks. All participants are followed every month for 6 months.