Cigarette smoking poses a serious but preventable health risk. Behavioral smoking cessation interventions have been show to help persons quit smoking. However, concerns about post-cessation weight gain have been reported as a significant barrier to quitting for many smokers. Recently, a new serotonin and norepinephrine reuptake inhibitor, sibutramine has received FDA approval to help persons lose weight. Given sibutramine effects neurotransmitters that are important in regulation of body weight, it is reasonable to hypothesize that this drug will decrease post-cessation weight gain in overweight and obese smokers who quit smoking. To date, there has been no clinical trial comparing use of sibutramine to a placebo, as pharmacologic therapy for reduction of post-cessation weight gain among overweight and obese smokers who take part in a behavioral smoking cessation program. Therefore, whether sibutramine is efficacious in reducing post-cessation weight gain in these smokers in unknown. Further, given the neuropharmacologic effects of sibutramine, it is reasonable to speculate that this medication could also be effective in helping smokers quit smoking both initially and long term. We hypothesize that use of sibutramine as compared to use of a placebo will result in a decrease in post-cessation weight gain in overweight and obese persons who quit smoking and result in an increase in smoking cessation rates. We plan to test these hypotheses in this double blind clinical trial by randomizing overweight and obese persons who smoke to one of two groups: Group 1) Sibutramine plus a behavioral smoking cessation program or Group 2) Placebo Sibutramine plus a behavioral smoking cessation program. We will determine post-cessation weight change and smoking cessation initially (during treatment) and long term (12 months after randomization, which is 9 months off study medication).