In this double-blind, placebo-controlled smoking cessation treatment study, 608 participants were randomly assigned to receive active bupropion and active 4-mg gum (AA, n = 228), active bupropion and placebo gum (AP, n = 224), or placebo bupropion and placebo gum (PP, n = 156). Relative to the PP group, the AA and AP groups were each significantly more likely to be abstinent at 1 week, end of treatment, and 6 months but not at 12 months postquit. After the first week postquit there were no differences in abstinence rates between the AA and AP groups. We found no significant individual difference variables that moderated outcome beyond 1 week postquit.