To illustrate the impact of westernization of lifestyle on the development of pre-clinical atherosclerosis in Japanese people, we compared risk factors for atherosclerosis such as serum lipids, blood pressure, BMI, insulin resistance, and smoking habits between non-diabetic native Japanese and non-diabetic Japanese Americans. Two hundred and twenty two non-diabetic Japanese Americans living in Hawaii and 271 non-diabetic Japanese living in Hiroshima, Japan were studied. Carotid intima-media wall thickness (IMT) was measured in all subjects by one physician. For all measurements the same ultrasound instrumentation was used. Although no significant differences were seen in serum total cholesterol (TC), triglycerides, or LDL-cholesterol (LDL-C) levels between the two groups in the 1998 study, previous to 1998 these three parameters were significantly higher in Japanese Americans than native Japanese in our study which has spanned the past 20 years. IMT was significantly greater in Japanese Americans than native Japanese (1.20+/-0.03 mm vs. 0.98+/-0.03 mm, (mean+/-S.E.) respectively; P<0.0001). Moreover Japanese Americans reach an IMT of 1.1 mm at age 50, whereas the native Japanese reach this value at age 70. These observations indicate more rapid atherosclerosis progression in Japanese Americans. Based on our IMT measurements, the status and the estimated progression of atherosclerosis in Japanese Americans is increased. Since IMT is a validated endpoint for assessment of atherosclerotic disease risk, it can be concluded that Japanese Americans are at increased risk for cardiovascular disease.