Purpose: This study, was undertaken to examine the presence of interleukin-1 receptor antagonist (IL-lra), IL-IO, and transforming growth factor-β1 (TGF-β1) in the synovial fluid (SF) lavage specimens of patients with temporomandibular disorders (TMDs) Patients and Methods: Synovial fluid lavage specimens were obtained from 14 temporomandibular joints (TMJs) of 12 patients with TMJ intermal derngement (ID) and 17 TMJs of 15 patients with TMJ osteoarthritis (OA). Seven synovial fluid lavage samples of TMJs of four asymptomatic donors served as normal controls. The concentrations of IL-lra, IL-10, and TGF-β1 were detected with sensitive and specific sandwich enzyme-linked immunosorbent assay (sandwich-ELISA). Results: IL-Lra, IL-10, and TGF-β1 in all the normal controls were undetecrtable. IL-lra concentrations were 175.78±52.43pg/mL in the patients with TMJ ID and 187.85±59.51pg/mL in those with TMJ OA IL-10 was undetectable in all the TMJ ID and OA samples. The concentration of TGF-β1 in TMJ ID patients (47.93±88.25pg/mL) was significantly less than in patients with TMJ OA (143.61±108.O0pg/mL) (P<01) Conclusion: The results suggest that deficiencies of IL-lra, H-10, and TGF β1 probably play an important role in the cause and pathogenesis of TMJ ID and OA.