Whether 24-hour aortic as opposed to brachial blood pressure (BPb) adds to the ability of 24-hour BP to predict cardiovascular damage is uncertain. We imputed 24-hour central aortic pulse pressure (PPc) from an equation derived in 1179 participants. We showed that the relationship between the in-office PPc imputed using this equation and the radial pulse wave-derived PPc (SphygmoCor software) had an r2=0.96 and a mean difference (±2xSD) of -1.4±6.2 mm Hg. In 485 participants 24-hour brachial systolic BP (SBP), imputed PPc and the aortic-to-brachial amplification ratio (PPb/PPc) were associated with echocardiographic left ventricular mass indexed to height2.7 (LVMI) (r=0.28, r=0.37 and r=-0.39 respectively, p<0.0001 for all). However, the unadjusted relationship between 24-hour PPb/PPc and LVMI was stronger than that between 24-hour SBP and LVMI (p<0.05 for comparison of relations). In addition, the effect size (standardized β-coefficient±SEM) of the unadjusted relations with LVMI were greater (p<0.05) for 24-hour PPb/PPc (β=-0.40±0.04), than for 24-hour SBP (β=0.28±0.04). Twenty-four hour PPb/PPc and 24-hour PPc were associated with LVMI independent of 24-hour SBP (r=-0.30, p<0.0001; r=0.24, p<0.0001 respectively), and the strength and effect size of the unadjusted relations with LVMI were greater (p<0.005) for 24-hour PPb/PPc (β=-0.34±0.05) than for 24-hour SBP (r=0.11, p<0.05; β=0.12±0.05). Marked differences in LVMI (mean±SD in g/m2.7) were noted across quintiles of 24-hour PPb/PPc even with adjustments for confounders including 24-hour SBP (quintiles 1: 48.2±17.3; 2: 42.7±14.1; 3: 42.4±13.2; 4: 41.4±13.7; 5: 39.6±16.9; p<0.01 for quintile 1 versus quintiles 2-5). With adjustments including 24-hour SBP, quintile 1 of 24-hour PPb/PPc, showed an 8.6 g/m2.7 higher LVMI than quintile 5 (p<0.005). Importantly, the strength and effect size of the unadjusted correlations with LVMI were lower (p<0.05) for the in-office PPb/PPc derived from radial pulse wave analysis (r=-0.25, p<0.0001; β=-0.24±0.04, p<0.0001) than for 24-hour PPb/PPc (r=-0.39, p<0.0001; β=-0.40±0.04, p<0.0001). In conclusion, 24-hour PPb/PPc derived from imputed aortic BP values identifies LVMI better that does 24-hour BP or the in-office PPb/PPc.