The aim of the present study was to evaluate the effect of dihydropyridine calcium antagonist isradipine on left ventricular (LV) structure and function in patients with essential hypertension. Cuff blood pressure and Doppler echocardiographic variables were assessed in 26 patients with mild to moderate hypertension (diastolic blood pressure range 95-110 mmHg) before and after 12 weeks of therapy with either isradipine 5 mg daily or enalapril 20 mg daily. The study was of double-blind, parallel design, with a placebo run-in period of 15 days. Three subjects withdrew from isradipine treatment because of flushing and 2 from enalapril treatment due to cough before completing the study. Both drugs significantly reduced cuff systolic and diastolic blood pressure (p < 0.001) without affecting heart rate. By virtue of the decrease in both septal wall (p < 0.01) and posterior wall thicknesses (p < 0.05), isradipine treatment produced a significant reduction in LV mass adjusted for height (p < 0.001) in comparison with placebo; also LV end-systolic dimension showed a slight decrease (p < 0.05). Enalapril induced a similar reduction in LV end-systolic dimension (p < 0.05) but the changes of wall thickness and LV mass did not reach statistical significance. In conclusion, our results indicate that isradipine treatment improves LV systolic function and causes a significant reduction in LV mass. This reduction is observed early in the course of antihypertensive treatment and is effective in both patients with and without LV hypertrophy.