Cigarette smoking as a risk factor for cerebro- and cardiovascular diseases was studied in a long-term prospective population survey which has been carried out in a Japanese rural community, Hisayama. In this population, the incidence of thrombotic brain infarction (TBI) was much higher than that of coronary heart disease (CHD) over a 26-year follow-up period. Cigarette smoking was strongly related to the occurrence of CHD but not to TBI. Comparing the incidence of CHD and TBI between first or early cohort (1961-74) and second or recent cohort (1974-87) during the 13-year follow-up, the incidence remained unchanged for CHD, while it significantly decreased for TBI in recent population. The prevalence of cigarette smoking as well as hypertension decreased in recent years, while hypercholesterolemia, obesity, and glucose intolerance increased. Smoking is a major contributor to CHD for men in both cohorts, but it is not any more for women in the recent cohort.