Vascular endothelial cells were marked with Evonymus europaeus agglutinin (EEA) in the major organs of 6 subjects to reveal the anatomical distribution of positive elements in the human after fixation in paraformaldehyde-lysine-periodate and embedding in paraffin. EEA may be used as a marker of human adult vascular endothelium in the same way as Ulex europaeus Agglutinin 1, revealing the same positive endothelial and epithelial territories. The intensity of labeling was constant in a given subject of the B blood group. In A or 0 individuals the cerebral endothelium showed a much lower reactivity than the cardiac endothelium. This lectin, equally active in higher mammals, offers the unique advantage of direct comparison between species.