African Americans (blacks) have a disproportionately high incidence of end-stage renal disease due to hypertension. The Modification of Diet in Renal Disease (MDRD) Study found that strict blood pressure control slowed the decline in glomerular filtration rate (GFR) only in the subgroup of patients with proteinuria. The present report compares the effects of blood pressure control in black and white MDRD Study participants. Fifty-three black and 495 white participants with baseline GFRs of 25 to 55 mL/min/1.73 m2 were randomly assigned to a usual or low mean arterial pressure (MAP) goal of < or = 107 or < or = 92 mm Hg, respectively. GFR decline was compared between randomized groups and correlated with the level of achieved blood pressure. The mean (+/-SE) GFR decline over 3 years in the low blood pressure group was 11.8+/-7.3 mL/min slower than in the usual blood pressure group among blacks (P=.11) compared with 0.3+/-1.3 mL/min slower among whites (P=.81) (P=.12 between blacks and whites). In both blacks and whites, higher baseline urine protein excretion was associated with a greater beneficial effect of the low MAP goal on GFR decline (P=.02 for both races). Combining both blood pressure groups and controlling for baseline characteristics, higher follow-up achieved MAP was associated with faster GFR decline in both blacks (P<.001) and whites (P=.002), with a sevenfold stronger relationship in blacks (P<.001). These secondary analyses support the prior recommendation for a lower than usual blood pressure goal (MAP < or = 92 mm Hg) in black and white patients with proteinuria (> 1 g/d). In addition, a lower level of blood pressure control may be even more important in blacks than in whites in slowing the progression of renal disease.