This longitudinal prospective study was designed to assess the effects of the angiotensin converting enzyme inhibitor (ACEI) ramipril on ventricular mass, left ventricle (LV) diastolic function and blood pressure in patients with mild to moderate essential hypertension and hyperinsulinemia. LV diastolic dysfunction is the first target organ alteration occurring in hypertensive patients, while ventricular hypertrophy is the most relevant predictive factor for cardiovascular morbility and mortality in systemic hypertension. Because several studies have demonstrated that there is no direct correlation between blood pressure values and the severity of LV hypertrophy or diastolic dysfunction, it is assumed that other factors are involved in the genesis of these functional alterations. Moreover, the hypertensive effect of insulin is caused by sympathetic stimulation, sodium and water renal retention and protooncogene stimulation leading to myocardial and vascular fibrosis and hypertrophy. We studied 24 hypertensive patients with hyperinsulinemia. All patients underwent an overall and cardiologic clinical evaluation, and electrocardiographic and ecocardiographic studies were performed at baseline and 6 months after being treated with 2.5 to 5 mg/day ramipril. Ramipril treatment significantly reduced systolic (12 mmHg) and diastolic (12 mmHg) pressure levels, basal insulin serum levels (23.62 pmol/dL vs 10.42 pmol/dL), and left ventricle mass index values (143.8 g/m2 vs 118.2 g/m2). Among the variables assessing LV diastolic function, only the transmitral flow E/A wave ratio showed significant differences in women. Ramipril was well tolerated and no significant adverse events were reported.