Japan had the highest mortality from stroke among developed countries in 1960, but experienced rapid changes in diet and other lifestyles with economic growth between the 1960s and the 1980s, which provided an unique opportunity to observe a natural experiment of changes in risk factors and stroke. Blood pressure levels declined due to improvements of drug treatment for hypertension and to dietary improvements such as sodium reduction. An increase in mean values of ethanol intake and body mass index did not correspond with a decline of blood pressure levels. Serum total cholesterol increased with an increased intake of meat, egg, milk and dairy products. Age-adjusted mortality rate of stroke declined 70% between 1960 and 1990. The changes of diet, blood pressure levels and stroke were more evident in rural populations than in urban populations. Risk factors of stroke has been investigated prospectively, and hypertension was found to be the most important risk factor. A low blood cholesterol was associated with the increased risk of intracerebral hemorrhage, which has been confirmed in several Japanese populations, Japanese Americans and Caucasian Americans. Thus, a rise in serum cholesterol suggested to contribute in part to a decline in intracerebral hemorrhage. Risk factors for cerebral infarction include age, atrial fibrillation and hypertensive endorgan effects such as resting electrocardiogram and fundscopic examination. A community-based hypertension control program for stroke prevention has been evaluated ; a larger decline in stroke incidence in the intervention community (69%) than in the reference community (49%, the difference : p<0.001). Effective community programs stimulated the formation of the 1982 national act on health and medical care in which every municipal government is required to conduct health screenings and education for residents aged 40 and over to prevent cardiovascular diseases. J Epidemiol, 1996 ; 6 : S43-S47.