There have been only a few investigational reports of sleep apnea syndrome (SAS) in patients with rheumatoid arthritis (RA), although it may not be a rare condition and may be life-threatening occasionally. The factor precipitating SAS in such patients is thought to be destruction of the temporomandibular joints (TMJs) from RA processes. To assess the relationship of the degree of destruction of the TMJs to the frequency of apnea, we examined them in 10 RA patients who complained of snoring. Those patients were classified as classical RA according to the criteria of American Rheumatism Association. They consisted of 3 males and 7 females with a mean age of 57.8 + 11.0 years and a mean disease duration of 15.9 +/- 9.4 years. In order to numerically evaluate the degree of destruction of the mandibular rami, we quoted a method from the literature (Redlund-Johnell I, Scand J Rheumatol 16:355, 1987) and measured the vertical distance (= ramal height) from the mandibular angle to the palato-occipital line on the lateral view film of the cervical spine in each patient. The mean values of ramal height (RH) of the normal material (we studied in Japanese) are 46.0 mm in males and 38.3 mm in females. There were 8 cases of SAS out of the 10 RA patients studied. Their mean total apneic episode (TAE) was 289.9 mm with a range of 0-611. The mean ratio (%) of RH to mean value of the normal material (%RH) was 68.8 +/- 22.2% for all. There was a significant statistic correlation between TAE and %RH (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)