Long-term impact of smoking cessation on the incidence of coronary heart disease. Using a simulation model of the US male population, we estimated the long-term impact that future smoking cessation programs would have on the distribution and occurrence of coronary heart disease in males ages 35-84. For interventions that reduce the number of smokers by 25 percent in 1990, the number of men free of coronary heart disease is projected to increase by 416,787 (0.7 percent) in 2015, and the age-standardized absolute incidence to decline by 2.3 percent. Incidence rates and absolute incidences are projected to fall in men under age 65, but absolute incidence would rise in men over age 65, in large part because of the increased number of men who were at risk for coronary heart disease because of a reduction in non-coronary smoking-related mortality. These trends were more marked for greater smoking reductions and were generally unaffected in a variety of analyses using alternative assumptions, which considered smoking as a risk factor in the elderly, a lag-time before benefits from smoking cessation were realized and secular declines in smoking prevalence. Subject to the assumptions of our model, we conclude that smoking reductions will markedly reduce coronary heart disease, especially in younger age groups, and that this benefit will be slightly offset by a small increase in absolute incidence in elderly men. 