Temporomandibular joint (TMJ) involvement in rheumatoid arthritis (RA) is not uncommon. In this study a questionnaire, clinical assessment, and high resolution computerized tomography (HRCT) were used in 15 patients with rheumatoid arthritis to evaluate the diagnostic criteria of TMJ involvement. Symptoms due to TMJ involvement were present in 33.3% of the patients. Frequency of involvement was 40.0% on clinical assessment but 86.6% with HRCT assessment. The most common HRCT findings were decreases in the joint space (33.3%), mandibular subchondral cysts (23.3%), temporal subchondral cysts (23.3%), degeneration (23.3%), shape (13.3%) and height (13.3%) anomalies of the mandibular condyle, condylar head resorption (13.3%), erosion of the mandibular condyle (13.3%), and demineralization (13.3%). All patients with positive clinical findings also had positive HRCT findings. In seven (46.7%) of the patients, there were no symptoms or clinical findings implying TMJ involvement; however, they had positive results on HRCT evaluation. The HRCT findings may be the initial sign of TMJ involvement in patients with rheumatoid arthritis. In conclusion, it is suggested that RA patients with the suspicion of TMJ involvement should undergo HRCT evaluation, because HRCT findings may precede the clinical findings.