To examine the effect of smoking cessation on cardiovascular disease mortality in Asians, the authors conducted a 10-year prospective cohort study of 94,683 Japanese (41,782 men and 52,901 women) aged 40-79 years who were part of the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC Study). During 941,043 person-years of follow-up between 1989-1990 and 1999, 698 deaths from stroke, 348 from coronary heart disease, and 1,555 from total cardiovascular disease occurred in men and 550, 199, and 1,155, respectively, in women. For men, the multivariate relative risks for current smokers compared with never smokers were 1.39 (95% confidence interval (CI): 1.13, 1.70) for stroke, 2.51 (95% CI: 1.79, 3.51) for coronary heart disease, and 1.60 (95% CI: 1.39, 1.84) for total cardiovascular disease. The respective relative risks for women were 1.65 (95% CI: 1.21, 2.25), 3.35 (95% CI: 2.23, 5.02), and 2.06 (95% CI: 1.69, 2.51), with larger excess risks for persons aged 40-64 years than for older persons. The risk decline after smoking cessation occurred for coronary heart disease and total cardiovascular disease within 2 years and for total stroke after 2-4 years. For each endpoint and in both age subgroups of 40-64 and 65-79 years, most of the benefit of cessation occurred after 10-14 years following cessation. Findings imply the importance of smoking cessation at any age to prevent cardiovascular disease in Japanese.