Black-white differences in the association between antihypertensive therapy, continuous measures of mean arterial and pulse pressures and left ventricular (LV) mass estimated from a multivariable electrocardiographic algorithm were examined in 6,020 men (23% black) and 7,970 women (29% black) participating in the Atherosclerosis Risk in Communities (ARIC) study. Mean arterial and pulse pressures, weight, the percentage of subjects taking antihypertensive medication, and LV mass were higher in black than in white men (98 vs 89 mm Hg, 47 vs 46 mm Hg, 188 vs 187 pounds, 30% vs 17%, and 243 vs 217 g, respectively). Results of similar direction but greater magnitude were observed in black versus white women (mean arterial pressure, 94 vs 85 mm Hg; pulse pressure, 50 vs 47 mm Hg; weight, 180 vs 153 pounds; percent treated, 42% vs 18%; and LV mass, 203 vs 169 g, respectively). In multivariable regression analyses, blacks had higher levels of LV mass, and LV mass increased more sharply with increasing mean arterial pressure in blacks than in whites after adjusting for age, pulse pressure, and weight. At equal mean arterial and pulse pressures, age, and weight, treated blacks had higher LV mass than treated whites. These data indicate that blacks have higher LV mass than whites, and a more pronounced blood pressure-LV mass relation after controlling for other risk factors and treatment status. Given the prognostic importance of LV hypertrophy,