To explore the racial differences in blood pressure levels in American youth, and to extend current data to include youth of Asian, black, Hispanic, and non-Hispanic white descent, we recorded blood pressures among ninth graders during the spring of the years 1985 to 1989 in a suburb of Los Angeles. Trained observers, following a standardized protocol, obtained blood pressure measurements from 4577 students (39% black, 30% Hispanic, 21% white, 10% Asian; 50% female) with a mean age of 15 years. With the use of age- and sex-specific 90th percentiles reported in 1987 by the Second Task Force on Blood Pressure Control in Children to define elevated blood pressure, the prevalence of elevated systolic blood pressure (SBP) was 8.1% (diastolic blood pressure (DBP), 9.3%) among female subjects and 16.0% (DBP, 18.5%) among male subjects. Comparisons of the prevalence of elevated blood pressure among ethnic-racial groups within sexes were statistically significant only for Asian girls (SBP, 13.1%; DBP, 14.0%) relative to other female subjects (SBP, 7.6%, p < 0.005; DBP, 8.8%, p < 0.01); these differences persisted after adjustment for body height and body mass index. A similar trend for Asian boys was apparent only for DBP (23.0% vs 18.0%, p = 0.065). Results for group means were comparable: average SBP and DBP were higher for Asian girls than for other ethnic groups. In addition, boys in this sample may have higher blood pressure than boys from other areas of the country. These results suggest that Asians in California may be at greater risk of having early development of hypertension.