In vitro lymphocyte adhesion to, and selective radiosulphate uptake by, endothelial cells has been demonstrated in chronically inflamed tissues of patients with peptic ulceration, rheumatoid disease, pilonidal sinus, autoimmune thyroiditis, polymyositis, primary biliary cirrhosis, and pyelonephritis. These characteristics have been described previously in endothelial cells functionally specialized for promoting lymphocyte traffic from blood to lymph node parenchyma. It is suggested that these observations indicate that some vessels in inflamed tissues may be, at least in part, responsible for the selective accumulation of lymphocytes within the tissue. Manipulating the development of this type of vessel may offer a novel way of influencing the progress of inflammatory disorders.