The effectiveness of Biarison vs. placebo was compared in an inter-individual double-blind study on 30 hospitalized patients with possible, definitive and classical rheumatoid arthritis. The time of comparison was 3 weeks; the dose used 900 mg (up to maximally 1500 mg)/day. The clinical index and the index of activity according to Lansbury were improved with Biarison and with placebo. The superiority of Biarison could be confirmed statistically (p less than 0,01). The effectiveness of Biarison was shown in reference to parameters of pain (number of painful joints and intensity of joint pain, pain on motion and at rest). Biarison was essentially well tolerated. Side effects were all gastro-intestinal. In 3 patients adverse reactions were slight and subsided spontaneously when treatment was continued. In 2 individuals Biarison had to be withdrawn in the 3rd week of treatment. In the placebo group 3 patients were taken off treatment due to no therapeutic effectiveness.