Symptoms and signs of rheumatoid arthritis vary within the day and from day to day. Interesting and possibly important observations can be missed when evaluations are based only on outpatient measurements, which are likely to be made at only one time and at infrequent intervals. We have found that patients can measure their own grip strength and finger joint sizes at home, and simultaneously assess overall pain and stiffness on numerical scales. Measurements made by patients were reproducible when made at the same time of day if on the same treatment. The patient's subjective assessment of pain and stiffness is a useful measure of the severity of rheumatoid arthritis. These pain and stiffness ratings were found to be well correlated with the patient's objective measurements of finger joint size and grip strength. Information not otherwise available can be collected by studying patients at home with these self-measurement techniques. These have allowed the demonstration of circadian variations in the signs and symptoms of rheumatoid arthritis and improved the evaluation of drugs studied in clinical trials.