Aim: To evaluate the impacts of ambulatory pulse pressure (PP) and office PP on left ventricular hypertrophy(LVH) in patients with essential hypertension. Methods: Totally 337 initially untreated subjects with mild to moderate essential hypertension were included in this study. All subjects took office PP 3 times measurements in different days, ambulatory blood pressure(BP) monitoring and echocardiography. 1 Subjects were divided into four groups according to their ambulatory PP levels and into five groups according to their office PP levels. The results were compared respectively. 2 They were further divided into LVH group and non-LVH group according to the degree of left ventricular mass index(LVMI). Results: Both ambulatory and office PP were significantly correlated with age, history of hypertension, LVMI, arterial stiffness index (ASI) and 24-hour heart rate(HR). Arterial stiffness evolved progressively with PP increase, and its correlation with ambulatory PP was much more significant than office PP(r = 0.670, P < 0.01 vs r = 0.399, P < 0.01). Ambulatory PP and 24 h systolic systolic blood pressure (SBP) were significantly higher in LVH group than in non-LVH group[(49.0 ± 10.2) mmHg vs (44.7 ± 8.9) mmHg, P < 0.001 and(132.1 ± 13.1) mmHg vs (126.5 ± 12.7) mmHg, P < 0.001(1 mmHg = 0.13 kPa ]; Ambulatory PP was associated with LVMI much stronger than office PP (r = 0.277, P < 0.01 vs r = 0.105, P < 0.05). Conclusion: The increase of PP is an important determinant of LVH. Compared with office PP, the ambulatory PP provides a more precise estimate of target organ damage upon hypertension.