The distribution of cell adhesion molecules (CAMs) and matrix proteins in the normal synovium of four subjects was studied by immunohistology in order to determine the factors governing the cellular and tissue organization of the intimal and subintimal compartments. Basement membrane proteins, laminin, and collagen type IV, as well as vitronectin and fibronectin, were identified in the intima and there was corresponding expression of integrin and non-integrin receptors (e.g., CD29, CD49b, CD49d, CD49e, CD49f, CD51, CD61, CD44) for these matrix proteins. There were notable differences in CAM expression between intimal, subintimal, and vascular compartments of the synovial membrane. Phenotypic heterogeneity for CAMs involved in cell-cell interactions, particularly CD11a, CD11b, ICAM-1, and HLA-DR, was also present. The range of CAMs expressed by synovial and endothelial cells not only indicates a structural role for these antigens, but also suggests that they may control leucocyte traffic into the membrane, including recruitment of cells into the synovial lining.