The function of endothelium is the lining of the vessel wall and the control of vascular permeability, homeostasis and leukocyte emigration from the blood into the surrounding tissue. Different adhesion molecules expressed in a coordinated and regulated way control this function. In this review, we discuss adhesion molecules involved in endothelial junctions and their involvement in leukocyte transendothelial migration. Passage of the leukocyte across the endothelium appears to require delocalization of certain vascular adhesion molecules whereas other molecules interact directly with leukocyte ligands. Understanding of the function of vascular adhesion molecules is further complicated as they transduce signals to the endothelium and interact with the cytoskeleton and adaptor proteins.