Glycoproteins expressed on the luminal surfaces of microvascular endothelium derived from various murine organs were analyzed and compared with those expressed by cultured vascular endothelial cells. Cell-surface vascular proteins were radiolabeled in situ via intracardiac perfusion with lactoperoxidase/Na125I. Autoradiography confirmed that the radiolabel was restricted to the vessel lumen in most tissues. Controls contained 125I-labeled serum proteins to identify adsorbed serum components. Glycoproteins were analyzed by western enzyme-linked lectin analysis using detergent extracts of 125I-labeled microvessels isolated from different organs. The western transfers were probed with a panel of lectin-peroxidase conjugates to determine differences in protein glycosylation. The same transfers were also screened for exposed 125I-labeled cell-surface proteins by autoradiography. This dual analysis detected glycoprotein patterns unique for each organ. At least seven major proteins (Mr approximately 180 K, 130 K, 95 K, 80 K, 75 K, 60 K, 12 K) were common to microvessels derived from each organ; however, certain glycoproteins appeared to be expressed differentially in particular organs. For example, a Mr approximately 135 K WGA-binding glycoprotein was detected in brain microvessels, whereas another WGA-binding glycoprotein of Mr approximately 40 K was detected only in kidney. In lung microvessels, a Mr approximately 140 K WGA binding glycoprotein and a Mr approximately 55 K RCA-I-binding galactoprotein were expressed preferentially, and liver microvessels displayed Mr approximately 220 K protein and a Mr approximately 35 K PNA-binding galactoprotein. The cell-surface-iodinated protein profiles from in situ labeled microvessels were similar to profiles derived from cultured bovine aortic endothelial cells and several short-term endothelial cell cultures isolated from different organs. The results from this study suggest that organ-associated endothelia express glycoprotein fingerprints unique to each organ.