The Second Australian National Blood Pressure Trial reported better prognosis for hypertensive subjects randomly assigned to an angiotensin-converting enzyme inhibitor (ACE-I) compared with a diuretic-based regimen despite no difference in brachial blood pressure control. A possible explanation is that there was a difference in central aortic pressures despite similar brachial pressure reductions. We examined this hypothesis in a subset of the Second Australian National Blood Pressure Trial cohort evaluated both before and after 4 years of treatment. The average age of the 479 subjects was 71.6 +/- 4.7 years (mean +/- SD), and 56% were women. Brachial systolic and pulse pressures after treatment were 145 +/- 1 (mean +/- SEM), 143 +/- 1, 72 +/- 1, and 70 +/- 1 mm Hg for diuretic and ACE-I groups, respectively. The respective changes from pretreatment values were -17 +/- 2, -16 +/- 2, -9 +/- 1, and -7 +/- 1 mm Hg. None of the differences between diuretic and ACE-I groups were significant. Central arterial pressure waveforms were acquired from carotid tonometry and calibrated from brachial pressures. Central systolic and pulse pressures posttreatment were 144 +/- 2, 144 +/- 2, 71 +/- 2, and 72 +/- 2 mm Hg for diuretic and ACE-I groups, respectively. The respective changes from pretreatment values were -15 +/- 2, -17 +/- 2, -6 +/- 2, and -8 +/- 2 mm Hg. None of the differences between diuretic and ACE-I groups were significant. The similarity of central and brachial pressures in this cohort of older hypertensive subjects is most likely because of the influences of age and hypertension in increasing arterial stiffness. There is no evidence that the better prognosis for patients randomly assigned to ACE-I in Second Australian National Blood Pressure Trial resulted from a disproportionate lowering of central blood pressure.