The effects of three doses of perindopril (4.8 and 16 mg), a new angiotensin I-converting enzyme inhibitor, and of a placebo on systemic blood pressure, heart rate, brachial artery flow and diameter, forearm vascular resistance and the renin angiotensin system biological parameters (plasma converting enzyme activity PCEA, renin activity PRA and aldosterone PA) were compared during a double-blind cross-over study performed in six healthy volunteers. Perindopril dose-dependently inhibited PCEA, increased PRA, augmented brachial artery flow and diameter and decreased forearm vascular resistance, whereas it did not affect systemic blood pressure and heart rate. The perindopril-induced increase in brachial artery flow was related (a) at the low dose to the sole arteriolar and (b) at the two highest doses to both arteriolar and large vessels dilatation. Finally, during the ten first hours following drug intake, there was a significant correlation between perindopril-induced PCEA inhibition and brachial artery flow increase.