In the immune system, the lymphatic vasculature serves several key functions, including leukocyte traffic and transfer of antigens and signaling molecules. Lymphatic endothelial cells (LECs) form the blind-ended terminals of initial afferent lymphatic capillaries, and line the inner surface of collecting lymphatic vessels, subcapsular, medullary and other sinuses of lymph nodes, and efferent lymphatic vessels. LECs use cell surface-expressed adhesion molecules from many super families for multiple different purposes. At sites of endothelial-to-endothelial contacts, adhesion molecules of LECs regulate the development of semipermeable button-type junctions in the initial lymphatics, and the formation of tight zipper-type junctions in larger collecting lymphatics. Moreover, LECs adhere to the surrounding cells and extracellular matrix via integrins and cadherins, and in addition, form specific anchoring filaments, which help to keep the lumen of the initial lymphatics patent. Very importantly, lymphocyte and dendritic cell traffic to and from the lymphatic vessels is an active process, and several endothelial adhesion molecules, in concert with chemotactic signals, are known to regulate leukocyte intravasation to and extravasation from the lymphatic vasculature.