The purpose of this prospective, randomized controlled study was to determine the efficacy of an intensified, late pregnancy, smoking cessation intervention for resistant pregnant smokers (n = 269). Participants received 3-5 min of counseling plus a self-help booklet at their first prenatal visit and seven booklets mailed weekly thereafter; at 28 weeks, all had been smoking in the past 28 days. The experimental group received a stage of change-based, personalized feedback letter and two telephone counseling calls using Motivational Interviewing (MI) strategies. The control group received care as usual. The 34th week cotinine data demonstrated no overall difference between groups. However, an implementation analysis suggested that 43% of women who received the full intervention (E2) were classified as not smoking compared to 34% of the control group. At 6 weeks postpartum, 27.1% of the E2 group reported being abstinent or light smokers vs. 14.6% of the controls. No differences were detected at 3 and 6 months postpartum. Results lend preliminary but very modest support for this intervention with resistant pregnant smokers. Improvements in the intervention and implementation issues are discussed.