BACKGROUND No studies have been conducted in Asia to examine predictors for smoking cessation by long-term follow-up of smokers. We sought to examine predictors for smoking cessation in Japanese subjects using baseline and 10-year follow-up data of the Japan Public Health Center-based Prospective Study (JPHC Study) Cohort I. METHODS We calculated adjusted odds ratios of predictors for smoking cessation with a cohort of 9,524 Japanese men and women aged 40-59 years who were smokers at baseline (1990) and for whom smoking status information at 10-year follow-up (2000) was available. RESULTS At follow-up, 24.9% of smokers had stopped smoking. White-collar workers were more likely to cease than blue-collar ones; the multivariate odds ratio (OR) was 1.18 (95% CI: 1.05-1.32). The multivariate OR of smoking cessation for initiation of a prescribed drug and that of disease development was 1.92 (95% CI: 1.72-2.14) and 1.21 (95% CI: 1.08-1.36), respectively. Those smoking more cigarettes and who started smoking at a young age were less likely to stop smoking. Older age, physical activity, and participation in health checkups were associated with smoking cessation. Gender was not a significant predictor after adjustment for other factors. CONCLUSIONS In a large follow-up study of middle-aged Japanese smokers, the predictors of smoking cessation were age, job, smoking habit, physical activity, health checkup participation, and health status.