Japanese Americans have experienced a higher prevalence of type 2 diabetes than in Japan. Research conducted in Seattle suggests that lifestyle factors associated with 'westernization' play a role in bringing out this susceptibility to diabetes. These lifestyle factors include consumption of a diet higher in saturated fat and reduced physical activity. A consequence of this is the development of central (visceral) adiposity, insulin resistance, and other features associated with this insulin resistance metabolic syndrome, such as dyslipidemia (high triglycerides, low HDL-cholesterol, and small and dense LDL particles), hypertension, and coronary heart disease. We have postulated that the superimposition of insulin resistance upon a genetic background of reduced beta-cell reserve results in hyperglycemia and diabetes among Japanese Americans. This article reviews evidence that support this view.