Objective: To assess the relationship between left ventricular hypertrophy (LVH) or left ventricular geometry (LVG) and endothelial function in patients with essential hypertension (EH). Methods: Seventy-six patients and 30 normal subjects were first examined by echocardiography. Brachial artery dilatation induced by reactive hyperemia (DIRH) or nitroglycerin (DING) was detected using high-resolution ultrasonography. Results: DIRH was lower in patients with hypertension than in the controls, and the decrease in DIRH was greater in the patients with LVH than that in patients without LVH (4.36±2.54% vs 8.56±1.87 %; P < 0.0001). There were no significant differences in age, serum concentrations of total cholesterol, triglycerides or sugar, blood pressure and the brachial artery dilatation induced by nitroglycerin between the two groups (P > 0.05). While there was no significant difference in DIRH between the patients with normal left ventricular geometry or cardiac remodeling, the patients showing either eccentric or concentric left ventricular hypertrophy had lower DIRH than the patients with normal left ventricular geometry or cardiac remodeling. The DIRH was the lowest in patients with concentric hypertrophy. Although bivariate analysis showed that the left ventricular mass index (LVMI) correlated well with the brachial artery dilatation induced by reactive hyperemia, diastolic blood pressure and mean blood pressure (r=-0.61, P < 0.0001; r=0.27, P < 0.05; r=0.31, P < 0.05, respectively), a multivariate stepwise regression demonstrated that LVMI correlated only with the brachial artery dilatation induced by reactive hyperemia. Conclusion: Left ventricular hypertrophy was related to endothelial dysfunction in essential hypertension. The endothelial dysfunction might be basic and important in the progression of left ventricular hypertrophy.