Objective. To investigate the role of EDAcontaining fibronectin (EDA+ FN), a splice variant of FN detectable in association with cellular transformation, in the adherence of synovial cells (SC) on rheumatoid cartilage surface.Methods. migration, wound healing, and oncogenic transformation (1). FN is mainly composed of 2 subunits of protein that each have a molecular weight of -250 kd and are connected by disulfide bonds near the carboxyl terminus (2) (Figure 1). Multiple isoforms of FN are produced from a single gene by alternative splicing at 3 distinct sites, EDA, EDB, and IIICS (3). FN produced by hepatocytes and commonly found in plasma, i.e., plasma FN (pFN), lacks the EDA and EDB regions. However, FN produced by most other tissues, i.e., cellular FN, contains the EDA and/or EDB regions of FN in various combinations (4).Previous studies have shown that the level of FN that contains the EDA and/or EDB regions is especially increased during the early stage of fetal development (5), malignant transformation (6), and wound healing (7). Furthermore, studies have indicated that the plasma level of EDA-containing FN (EDA+ FN) is increased in patients with vascular injury (S), malignant tumor (9), and, particularly, rheumatoid arthritis (RA) (10