['To evaluate the influence of mental stress on the neuroendocrine-immune system in patients with rheumatoid arthritis (RA).', 'Twenty-two patients with RA and 8 patients with osteoarthritis (OA) who underwent total knee or hip arthroplasties under general anesthesia were enrolled in the study. The blood levels of interleukin 6 (IL-6) and other substances related to stress were measured just before administering anesthesia on the day of the operation when the patients lay on the operating table and roughly 30 min later when the patients were under general anesthesia without mental stress. These values were compared with those at the same time on the day before the operation, which were considered the control levels.', 'In patients with RA, the levels of IL-6, cortisol, and epinephrine in the peripheral blood were significantly increased under mental stress, before anesthesia (p < 0.01). However, under general anesthesia, the IL-6, cortisol, and epinephrine were significantly decreased, compared with the levels before anesthesia (p < 0.01). Such changes were not apparent in patients with OA. The levels of other substances in the peripheral blood known to be related to stress, such as corticotropin-releasing factor, dopamine, and norepinephrine, showed no changes in patients with RA or OA.'] Do serum levels of interleukin 6 and stress related substances indicate mental stress condition in patients with rheumatoid arthritis?