Objective:The existence and localization of reninin situwas examined in human arteries under non-pathological conditions.Design:Biochemical and immunohistochemical procedures were adopted to examine the existence of renin in human gastroepiploic arteries using an antibody raised against human recombinant renin or a specific renin inhibitor.Methods:(1) Renin activity (angiotensin I generating activity sensitive to antihuman recombinant renin antibody or a specific renin inhibitor) in the homogenate of human gastroepiploic arteries with and without endothelium was compared; (2) vascular renin was immunohistochemically stained using a modified avidine–biotin–peroxidase complex method.Results:(1) Renin activity in human gastroepiploic arteries with endothelium was significantly higher than in those without endothelium; (2) immunoreactive staining selectively occurred in the endothelial cells of human gastroepiploic arteries.Conclusions:Renin is present in endothelial cells of human arteries under non-pathological conditions. Endothelial renin may play a role in the control of vascular tone through local production of angiotensin II.