Using the IL-6-dependent mouse hybridoma cell line KD 83, IL-6 biological activity in synovial fluids of the patients with Temporomandibular Joint Disturbance Syndrome (TMJDS) was tested. The results show that IL-6 level is high in 13 cases of 18 patients with TMJ degenerative changes and 5 cases of 12 patients with TMJ Disc Displacement. IL-6 level is less than 100 U/ml in all patients with Masticatory Muscle Disorder (59.4 +/- 29.4 U/ml). In addition, it has been found that TMJDS tends to have acute and chronic stages and IL-6 is probably related to acute stage of the patients.