Objective: To evaluate the efficacy and safety of a transdermal nicotine patch as an aid for smoking cessation in an over-the-counter setting. Design: Multicenter, double-blind, randomized, placebo-controlled trial of 6-week duration with 18 weeks of follow-up. Setting: Four shopping mall precincts. Participants: The randomized sample consisted of 802 adults (mean age, 39 years) and was 89% white and 54% female. A smoking history of at least 20 cigarettes per day for 1 year and a score of 5 (on a 10-point scale) on a motivational assessment questionnaire were required for enrollment. Poststudy follow-up was limited to those who had quit smoking at the end of 6 weeks. Intervention: Nicotine patches were provided at the shopping mall. Guidance consisted only of package instructions and a smoking cessation self-help booklet. Main Outcome Measures: Quit rates were defined as total abstinence from smoking for 4 consecutive weeks (treatment weeks 3-6), point prevalence smoking status at week 6, or nonsmoker at week 6 and week 24 (6-month postquit date). Smoking status mas assessed by diaries, and Verification for the first 2 quit rates was obtained by confirmation of carbon monoxide of 8 ppm or less in expired breath. Safety was evaluated by self-reported adverse events. Results: Quit rate was 12% for the active treatment group and 5.5% for the placebo group, based on total abstinence for 4 consecutive weeks (P = .001) compared with quit rates of 19.5% and 7.5% for active treatment and placebo groups, respectively, based on point prevalence data at week 6. At 24 weeks, 8.2% of nonsmokers in the active treatment group and 4.0% in the placebo group remained nonsmokers. At least 1 adverse event was reported by 57% receiving the nicotine patch and 39% receiving placebo (P<.001). Conclusions: When the nicotine patch was used in an over-the-counter setting, quit rates were comparable to those reported for medical settings. A 2:1 quit rate advantage was achieved at week 6 and was maintained at 24 weeks.