The aim of this study was to determine for teh first time the presence of the marker of oxidative stress N(epsilon)-carboxymethyllysine (CML) in RA synovial tissue from 10 patients with RA and 8 control subjects (4 of which had osteoarthritis (OA)) by immunohistology. It was found in the synovial lining, sublining and endothelium in all the RA and OA tissue samples, but staining was weaker in OA sublining vs RA. Some macrophages and T-cells were positive for CML. B cells were negative.