Histopathology demonstrating a manifest vasculitis is a rare event in synovial tissue (ST) from patients with chronic inflammatory joint disease. As a possibly more subtle sign of a vasculitic process, complement activation in vessels in ST was studied. In the same tissues, the expression of the adhesion molecules ICAM-1 and E-selectin in vessel walls was examined, to see if the expression was related to vasculitic processes. The study was performed by use of direct immunofluorescence technique on cryostat sections of ST, using mouse monoclonal antibodies to the terminal complement complex (TCC, C5b-9), ICAM-1 and E-selectin. Expression of ICAM-1 was found in the vessel walls in all of 28 tissues tested, whereas E-selectin was found in 4 cases and TCC in 11. E-selectin and TCC were found together in only 1 tissue. The study supports the view that ICAM-1 is always, or nearly always, present in vessel walls in synovial tissue from patients with chronic inflammatory joint disease. E-selectin and TCC may also be present, but the lack of association between these two proteins suggests that the mechanism leading to a complement mediated vasculitic process is different from that causing expression of E-selectin.