This will be a double-blind, placebo-controlled, pilot, randomized clinical trial. A total of 50 women who smoke and have regular menstrual cycles will be randomized to either progesterone (200 mgs BID) + Transdermal Nicotine Patch (TNP) or placebo + TNP for 8 weeks. TNP will be tapered after 4-6 weeks. Progesterone or matching placebo will be discontinued at the end of Week 8. All participants will also be provided behavioral treatment for smoking cessation. Participants will be inducted onto progesterone (or placebo) + TNP over a one-week period (Week 1) during the mid luteal phase, within a week before menses and the target quit date will be set for the 5 (+/-2) days after onset of menses. Participants will have post-trial follow-up visits at 1 and 3 months.The main study outcomes will be self- report of smoking abstinence, biochemically verified smoking abstinence, measures of cigarette craving and nicotine withdrawal, and measures of response inhibition.