The blood pressures and body sizes of children aged 10-15 years in the Minneapolis and St. Paul, Minnesota, public schools were measured during 1986 and 1987. The sample consisted of 1,680 Southeast Asian refugees--including 219 Cambodians, 1,086 Hmong, 149 Lao, and 226 Vietnamese--and 3,424 blacks and 11,336 whites. Mean systolic blood pressure in Hmong boys was higher than that in black boys and white boys. Mean systolic blood pressures of Hmong, Lao, and Vietnamese girls were lower than those of black girls and white girls. The mean diastolic blood pressures of Hmong boys and of Cambodian and Hmong girls were greater than those of blacks and whites of the same sexes. Southeast Asian children were shorter and weighed less than black children and white children. Body size may confound associations between ethnic groups and blood pressures and may obscure the problem of hypertension among the smaller Southeast Asian children. Southeast Asian boys had greater mean systolic blood pressures than did black and white boys across all weight strata; a similar contrast among girls did not reveal this difference. The risk of hypertension, defined by US National Heart, Lung, and Blood Institute guidelines, was assessed in multiple logistic regression analyses that controlled for differences in weight, height, age, and pulse rate. The odds ratios for hypertension, relative to blacks and whites of the same sexes, were 2.69 (95% confidence interval (CI) 1.85-3.65) in Hmong boys, 2.89 (95% CI 1.35-6.21) in Lao boys, 2.10 (95% CI 1.03-4.28) in Cambodian girls, and 1.49 (95% CI 1.00-2.20) in Hmong girls. Hypertension and subsequent cardiovascular disease may emerge as a significant problem among Southeast Asian refugees in the United States.