Whether changes in in-treatment 24-hour aortic blood pressure (BP) predict changes in left ventricular mass (LVM) in response to antihypertensive treatment better than 24-hour brachial BP is uncertain. We imputed 24-hour aortic pulse pressure (PPc) and the 24-hour aortic-to-brachial amplification ratio (PPb/PPc) from an equation that we derived in 1179 participants from a cross-sectional community study. Over a 4-month treatment period in 173 mild-to-moderate hypertensives, 24-hour BP decreased (change in systolic BP/diastolic BP=-22±16/-13±9 mm Hg, p<0.0001), 24-hour PPb/PPc increased (from 1.23±0.08 to 1.27±0.09, p<0.0001) and echocardiographic LVM indexed to height2.7 (LVMI) decreased (-8.8±14.4 g/m2.7, p<0.0001). In-treatment changes in neither 24-hour systolic BP (r=0.08, p=0.32) nor 24-hour PPc (r=0.12, p=0.13) were correlated with changes in LVMI. However, in-treatment increases in the 24-hour PPb/PPc amplification ratio were correlated with decreases in LVMI and these relationships were independent of changes in 24-hour brachial BP and persisted with adjustments for a number of confounders (partial r=-0.24, p<0.005). With or without appropriate adjustments, including baseline LVMI and 24-hour PPb/PPc, marked differences in the change in LVMI (mean±SD in g/m2.7) were noted across tertiles of the change in 24-hour PPb/PPc (Tertiles 1:-4.6±11.1; 2:-8.2±10.2; 3: -11.3±11.0, p<0.05 versus tertiles 1 and 2). With all adjustments including baseline LVMI and 24-hour PPb/PPc, a -6.7 g/m2.7 greater decrease in LVMI was noted in tertile 3 as compared to 1 for change in 24-hour PPb/PPc (p<0.005). In conclusion, the 24-hour aortic-to-brachial PP amplification ratio derived from imputed aortic BP predicts the regression of LVMI in response to antihypertensive treatment better than does 24-hour BP.