|| In an attempt to evaluate circulatory changes in patients with rheumatoid arthritis (RA), 20 patients with classical or definite RA as determined by ARA criteria and twenty healthy volunteers serving as control were randomly selected. None of the patients showed the clinical signs suggesting Raynaud's phenomenon. Thermograms as well as photoelectric plethysmograms were obtained solely from the right middle finger tip of each examinee. The whole hand was then immersed in the cold (10℃) water and kept there for one minute. After wiping away the wet hand with a dry towel very gently, we followed the sequential changes of the tempe· rature of the third finger tip and the period of time necessary for the tip to return to the original temperature prior to the cold water immersion was measured and expressed as 'return time' in minute. Before exposure to the cold, the mean values of temperature of the finger tips between the two groups were not significantly different. As opposed to the normal pattern in which one can find the warmest point at the finger tip and which was more frequently found in the control group of the current study, a type in which the distal part of the finger was much cooler than the proximal area (so-called 'distal cold type') was observed in 8 RA patients, whereas only four demonstrated this pattern in the control group. After brief exposure to the cold, eight out of 20 rheumatoid patients showed much prolonged return time (longer than 20 minutes), while only three of 20 controls remained with prolonged cool periphery, The difference between the two, however, was not statistically significant. Studies of the digital plethysmograph revealed that 70% of all the rheumatoids showed abnormal patterns: sclerotic and monophasic waves were discovered in 55% of the patients. In contrast, seventy percent of the normal control demonstra· ted normal wave pattern. Although the significant difference was not noted, the mean height of the systolic peak of the plethysmograph derived from the rheumatoid group tended to be much reduced, suggesting the reduced blood volume at the finger tips. Six RA patients and 13 normals who showed normal plethysmographic pattern before immersion in the cold water, demonstrated rapid return to the original temperature. Only in one normal control with a normal wave pattern, prolonged return time was observed, although the height of the systolic peak of the plethysmogram in this particular case was well within normal limit. Digital circulatory disturbance, however, was strongly suspected in eight RA patients with severely prolonged return time, They all showed abnormal wave patterns of the plethysmogram, including 2 cases with peripheral plateau wave, Markedly reduced heights of the systolic peaks were also demonstrated in all. Further elaborate studies including digital arteriography were indicated to implicate any organic change in the digital vessels, such as digital arteritis in RA first reported by Bywaters in 1957.