223 cases of definite rheumatoid arthritis were studied which were divided into ridaura treatment group and placebo group. Observations were made double-blind and prospectively. Judging from the comparison of therapeutic results of each treatment group on each clinical and laboratory parameters and of effective rate of each treatment group on the parameters and by comparing the physicians' and patients' assessments to the ridaura or placebo treatment, it was evident that the ridaura was much superior than placebo, possessing statistical significance. In physicians' assessment 14.2% failed to improve in the ridaura group but being 52% in the placebo group. Ridaura was a slow-acting drug, the earliest time for it to show clinical improvements being 2-4 months after medication. Adverse effects of ridaura were limited; incidence of loose bowel movements was much lower than that reported in the western countries. Among the 148 cases of the ridaura group, only two cases failed to complete the six months treatment course because of untoward reactions.