This study compared the effect of losartan and valsartan on left ventricular mass (LVM) and function in patients with untreated essential hypertension and concentric left ventricular hypertrophy (LVH). Thirty patients (17 men and 13 women; mean age, 48 +/- 8 years) with untreated essential hypertension and concentric LVH, as determined by echocardiographic assessment, were randomly assigned in equal numbers and double-blind fashion to receive either losartan 50 to 100 mg/d or valsartan 80 to 160 mg/d. Doppler echocardiograms were obtained from each patient before treatment, at the time of initial blood pressure control, and then after 6 months. A significant reduction (P< .01) in LVM index was observed in both the losartan group (from 57.1 +/- 7.2 g/m(2.7) to 51.5 +/- 6.1 g/m(1.7)) and the valsartan group (from 58.1 +/- 8.4 g/m(2.7) to 48.2 +/- 6.2 g/m(2.7)), but the reduction was higher (P < .05) in the valsartan group. The predicted midwall fractional shortening improved significantly in both the losartan group (from 81 +/- 8% to 89 +/- 9%, P < .05) and the valsartan group (from 78 +/- 7% to 91 +/- 9%, P < .01). Similarly, the early peak/peak atrial velocity ratio improved significantly both in the losartan group (from 0.78 +/- 0.4 to 0.88 +/- 0.3, P < .05) and the valsartan group (from 0.84 +/- 0.3 to 0.94 +/- 0.4, P < .01). These results indicate that valsartan is more effective than losartan in reducing LVM index in hypertensive patients with concentric LVH. This effect is associated with improvement in midwall systolic performance and left ventricular diastolic function.