The aim of this study was to assess the differential response in left ventricular mass and resistive index (RI) of renal and carotid arteries in mild to moderate essential hypertensive patients after 1 year of ACE inhibitor therapy. Twenty-six patients (mean age 42.9 +/- 10.9 years) underwent 24-hour ambulatory blood pressure monitoring, echocardiography and renal and carotid echo-Doppler (by measuring RI, as an expression of arterial impedance) after a placebo period and 12 months of fosinopril treatment (20 mg/day). Our study showed a significant decrease in 24-hour BP (p < 0.05), left cardiac mass (p < 0.05) and RI of common carotid and hilum renal arteries (p < 0.05). In contrast, there were no significant reductions in the interlobar renal RI (as an expression of unchanged intrarenal resistance) and in the internal carotid artery RI. While the 24-hour BP decrease was strongly correlated with the left cardiac mass modifications (r = 0.73, p < 0.005), no significant relationship was observed with the renal and carotid artery parameters. In conclusion, the present study demonstrated that long-term treatment with fosinopril produced a differential response in left ventricular mass and arterial RI in patients with mild to moderate essential hypertension. In addition, the arterial impedance modifications of common carotid and hilum renal artery were largely unrelated to the 24-hour BP reduction.