It is well recognized that African Americans have a higher prevalence of cardiovascular disease than White Americans although the underlying mechanisms are not entirely understood. This study was perfumed to evaluate racial differences in the chronotropic and vasodilatory effects of the beta-receptor agonist, isoproterenol. We compared cardiovascular responses to intravenous infusion of isoproterenol in 27 African Americans and 27 White men and women. African Americans showed significantly smaller beta 2-receptor mediated falls in diastolic pressure than Whites. In contrast, isoproterenol produced similar increases in heart rate in both races. The findings suggest that African Americans have decreased beta 2-receptor mediated vasodilatory capacity, and may help explain the higher prevalence of hypertension and cardiovascular disease in African Americans compared to Whites.