Arthritic temporomandibular joints were investigated for intra-articular temperature and joint fluid content of calcitonin gene-related peptide. Eleven patients (16 joints) with rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, or chronic unspecific polyarthritis or monarthritis participated in the study. The intra-articular temperature varied between 35.5 and 37.5 degrees C, with a mean of 36.5 degrees C. The concentration of calcitonin gene-related peptide varied between 7.5 and 749.0 pmol/l, with a mean of 108.6 pmol/l. There was a positive correlation between the intra-articular temperature and the joint fluid concentration of calcitonin gene-related peptide. The plasma level of the peptide was on an average 5% of the joint fluid level.