We performed immunohistochemical examinations on type II collagen-induced arthritis (CIA) mice, focusing attention on the changes in distribution of plasma proteins and extracellular matrix materials (ECM) and in expression of adhesion molecules. The limb joints of male DBA/1J mice immunized with bovine type II collagen were obtained at 6 to 20 weeks after the first immunization. In the early stage of CIA, deposition of fibrin, IgG, von Willebrand factor (vWF) and fibronectin was detected on the surface of the synovial lining layer and articular cartilage and in the articular cavity. In the stage of pannus formation, prominent proliferation of ICAM-1-positive capillaries and marked infiltration of LFA-1-positive neutrophils were observed in the pannus. The superficial portion of the pannus and basement membranes of proliferated capillaries were strongly positive for type IV collagen and laminin. In the late stage, the pannus invaded and destroyed articular cartilage and subchondral bone, and strongly positive immunostainabilities for both lysozyme and fibronectin were observed on the surface of the pannus and at the junctional portion between the pannus and the cartilage. The present immunohistochemical findings on the distribution of plasma proteins and ECM materials and the expression of adhesion molecules in CIA mice were similar to those in rheumatoid arthritis (RA) in many aspects. This suggests that CIA is a useful model for the investigation of RA.