Analyses were made separately for men and women of the predictors of end-of-treatment (4 months) smoking cessation and subsequent relapse at 12 and 24 months among 3,923 participants enrolled in the Lung Health Study's 12-week cognitive-behavioral group smoking cessation program. Nicotine gum (2 mg) was available to all participants. Men were more likely than women to quit smoking initially, but relapse rates were similar for both genders. Baseline variables associated with initial quitting for both genders included greater education, lower nicotine dependence, and fewer respiratory symptoms. The best predictor of relapse between 4 and 12 months was smoking at least 1 cigarette between quit day and 4 months. Nicotine gum use at 12 months predicted relapse by 24 months for both genders. Greater social and environmental support for quitting smoking were the only factors that predicted both initial quitting and relapse for both genders. Clinical implications are discussed.