The effects of cigarette smoking on cardiovascular disease were investigated in the Japanese community of Hisayama. This long-term prospective study assessed the occurrence of coronary heart disease and non-embolic cerebral infarction in relation to smoking habits at entry. The study population comprised 1603 subjects aged greater than or equal to 40 years. Seventy-six per cent of 699 men and 17% of 904 women were smokers. During 23 years of follow-up, 73 cases of coronary heart disease and 175 cases of non-embolic cerebral infarction developed. In both sexes, coronary heart disease occurred more frequently in those who smoked greater than 10 cigarettes per day than in those who never smoked. There was no relationship between smoking status and the incidence of non-embolic cerebral infarction. When more than one of the major risk factors (smoking, hypertension and elevated cholesterol) was present in the same person, the risk of coronary heart disease increased 2.4-7.7 times. Cox's proportional hazards model showed that cigarette smoking was an independent and significant risk factor for coronary heart disease, but not for non-embolic cerebral infarction.