Background: Observing longitudinal changes in smoking and drinking habits is important for evaluating the risk of incidence and death from cancer or other diseases in a cohort study. Methods: Smoking and drinking habits at baseline and about five years later among 18,312 males and 28,338 females were obtained from the baseline and interim surveys in the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC Study) sponsored by Monbusho (Ministry of Education, Science, Sports and Culture of Japan). Changes in smoking and drinking habits between the two Surveys were observed. Odds ratios for quitting these habits at interim survey were estimated. Results: Percentages of current smokers at baseline and interim surveys were 51.0% and 45.5% in males, and 5.2% and 4.8% in females, respectively. Percentages of current drinkers at baseline and interim surveys were 78.0% and 73.2% in males, and 29.5% and 23.5% in females, respectively. The number of cigarettes per day among male current smokers and the usual amount of alcohol consumed on each occasion among current drinkers decreased between the two surveys. Odds ratios for smoking cessation increased with age at baseline and decreased with the number of cigarettes per day at baseline. Odds ratios for drinking cessation increased with age at baseline and decreased with the usual amount of alcohol consumed on each occasion at baseline. Conclusion: The decrease in smoking and drinking habits was observed during the five-year follow-up period. Higher age and lower levels of exposure were associated with quitting smoking or drinking. Copyright © 2005 by Japan Epidemiological Association.