The reproducibility and sensitivity of quantitative infra-red thermography as a measure of peripheral joint inflammation was reassessed. Experiments were carried out in a temperature-controlled room at 20 degrees C. Initial stabilization experiments showed that in normal, medium sized, joints, there was an initial rapid cooling phase followed by a slower cooling phase which lasted longer than two hours. In the knees the differences between normal and active rheumatoid joints increased the longer patients remained in the room but for practical reasons a 30-minute stabilization period was subsequently chosen. In views of hands and fingers, rebound increases in skin temperature after entering the room, together with lesser differences between inflamed and non-inflamed joints, were found. The results suggested that the thermographic technique examined was adequate for detecting inflammatory changes in knee, ankles and elbows but unsatisfactory for quantification of inflammation in the small joints of the hands.