The detection of left ventricular (LV) hypertrophy on echocardiography is a powerful risk indicator in essential hypertension. However, the prognostic impact of LV mass values within the "normal" range and the shape of the relation between LV mass and prognosis remain unclear. Thus, 1925 white subjects with uncomplicated essential hypertension underwent off-therapy 24-hour blood pressure monitoring and M-mode echocardiography. During 4. 0+/-2 years of follow-up, there were 181 major cardiovascular events (2.4/100 patient-years) and 49 deaths from all causes. In the 5 gender-specific quintiles of LV mass distribution (partition values: 92, 105, 120, and 138 g/m(2) in men and 79, 91, 102, and 116 g/m(2) in women), cardiovascular event rates were 0.8, 1.7, 2.2, 2.9, and 4. 3 per 100 patient-years. After adjustment for several risk factors, including 24-hour ambulatory blood pressure, the relative risk (RR) of developing a cardiovascular event increased progressively from the first quintile (RR 1) to the second (RR 1.6, 95% CI 0.8 to 3.1), third (RR 1.9, 95% CI 1.01 to 4.0), fourth (RR 3.0, 95% CI 1.5 to 5. 8), and fifth (RR 3.5, 95% CI 1.8 to 6.8) quintile. For all-cause death, the RR in the fifth quintile compared with the first quintile was 4.3 (95% CI 1.2 to 13.4). In conclusion, the powerful relation between LV mass and risk of cardiovascular disease in subjects with uncomplicated essential hypertension is continuous over a wide range of LV mass values, even below the current "upper normal" limits. The relation remains significant after control for traditional risk factors, including ambulatory blood pressure.