Epidemiologic and pathologic studies were conducted between 1965 and 1986 to investigate trends for the incidence of coronary heart disease (CHD) and its risk factors in urban and rural populations and to relate the risk factor changes to trends for CHD incidence and pathologic findings. The epidemiologic study included men aged 4059 years who urban residents of Osaka. clerical and manual workers in Osaka, and rural residents of Akita prefecture. The pathologic study subjects were autopsied men aged 30 and over, admitted to a local hospital in Akita, whose autopsy rate was 88%. From a cohort of 8, 835 urban employees between 1975 and 1987, risk factors for myocardial infarction were identified: blood pressure, total serum cholesterol, blood glucose and cigarette smoking all which were compatible with findings in the US and European countries. For rural residents, serum cholesterol was less likely to be associated with the CHD incidence. Little contribution of serum cholesterol to development of coronary heart disease in rural men was supported by the pathologic study showing no significant association between serum cholesterol and the coronary atherosclerosis. Myocardial infarction from urban patients was characterized as massive necrosis in the myocardium with coronary artery stenosis and minimum atherosclerosis of basal cerebral arteries while that from rural men was small scattered necrosis in myocardium with atherosclerosis in both coronary and basal cerebral arteries. There was an increasing trend in the incidence of myocardial infarction in urban men but no change in rural men. The difference in the incidence trend can be attributed in part to differences in pathologic etiology and in blood pressure and serum cholesterol levels. Systematic surveillance is underway in both urban and rural population to clarify future trends for coronary heart disease and its risk factors.