Baseline echocardiography was performed on 25 patients with essential hypertension and a supine diastolic blood pressure of 95 to 114 mm Hg while receiving placebo. Once-daily trandolapril was then titrated from 1 to 4 mg. After 3 months of therapy, supine diastolic blood pressure decreased by 7.5% (p < 0.0001). Left ventricular hypertrophy regressed as evidenced by a 23.2% (p < 0.0001) decrease in left ventricular mass index at 3 months and a 12.4% (p < 0.05) reduction of relative wall thickness at 6 months. Although afterload decreased by 12.4% (p < 0.05) at 3 months, left ventricular systolic function remained unchanged, whereas left ventricular contractility, which was assessed from the load-independent relationship of end-systolic wall stress to velocity of circumferential fiber shortening, improved. Left ventricular diastolic function (E/A ratio) improved in 15 of 25 patients with low baseline values from 0.96 +/- 0.14 to 1.18 +/- 0.25 (mean +/- SD, p < 0.0002) at 3 months. We conclude that trandolapril effectively reduces left ventricular hypertrophy and improves diastolic function in patients with hypertension while systolic function is preserved.