We propose an 8-week, randomized pilot study to evaluate the safety and initial efficacy of progesterone. This will be a feasibility study that will compare progesterone to placebo for relapse prevention in 40 postpartum smokers. We will assess the feasibility and safety, including the potential effects on breastfeeding and infants exposed via breast milk, in addition to 7-day point prevalence of smoking abstinence after 8 weeks of treatment and at follow-up, 3-months after the end of the protocol.