THE AUTHORS STUDIED THE PREVALENCE AND RISK FACTORS of hypertension in samples of 2053 Japanese ages 40 to 70 in Hiroshima, Hawaii, and Los Angeles. The prevalence of hypertension (systolic blood pressure greater than or equal to 140 mmHg, diastolic blood pressure greater than or equal to 90 mmHg, or receiving antihypertensive drug treatment) was higher in Hawaii and Los Angeles for both sexes and almost all ages than in Hiroshima. The age- and sex-adjusted prevalence of hypertension in Hawaii, Los Angeles, and Hiroshima was 42.6%, 37.2%, and 29.7%. Hypertension was associated with a significant elevation in serum glucose, insulin, triglyceride, and total cholesterol levels in the combined participant population of Hawaii, Los Angeles, and Hiroshima. Age- and sex-adjusted mean values of serum total cholesterol, triglyceride, and insulin were highest in Hawaii and lowest in Hiroshima. The mean body mass index and 2-hour serum glucose levels were greatest in Hawaii and equal in the two other cohorts. These results suggest that hyperinsulinemia and hyperlipidemia may explain the prevalence of hypertension in the research participants.