 Varenicline, a nicotinic acetylcholine receptor partial agonist, has been shown in two placebo-controlled trials to be efficacious for smoking cessation. Given the high prevalence of nicotine dependence in bipolar disorder and the high prevalence of sub-syndromal and syndromal depressive symptoms in bipolar disorder, this 12-week adjunctive varenicline open label trial will be conducted to assess the feasibility, acceptability, and safety of varenicline in bipolar depressed smokers. All subjects will receive individual behavioral counseling. 