Previous studies have demonstrated significant ethnic differences in left ventricular structure in both normotensive and hypertensive subjects. To determine if these differences in ventricular geometry are associated with differences in vascular structure, we measured the minimum forearm vascular resistance in 30 healthy young African-American adults and in 30 whites matched for age, gender, and blood pressure. Average daytime blood pressure was determined by ambulatory monitoring during a typical work day. Minimum forearm vascular resistance was measured by plethysmography after 10 minutes of forearm ischemia. Indexed left ventricular mass and relative wall thickness were measured by 2-dimensional-directed M-mode echocardiography. The mean (+/-SD) ambulatory pressure was 126 +/- 11/79 +/- 8 mm Hg in African-Americans and 126 +/- 11/79 +/- 7 mm Hg in whites. The 2 groups were similar in body mass index and in family history of hypertension. African-Americans had a higher minimum forearm vascular resistance than did whites (2.39 +/- 0.75 vs 2.03 +/- 0.55 mm Hg, p <0.05). There was a trend toward a greater left ventricular relative wall thickness in African-Americans (0.38 +/- 0.07 vs 0.35 +/- 0.06, p=0.09). These results suggest that early vascular remodeling is present in African-Americans who do not have established hypertension, and that this ethnic difference in vascular structure is associated with a difference in ventricular geometry.