In 38 children with juvenile chronic arthritis the authors tested Sulphasalazine in an open clinical trial. The drug was administered for 26 weeks, 20-30 mg/kg/day. The action of the drug was followed up with regard to clinical (number of criteria of juvenile chronic arthritis, functional state, period of morning stiffness, number of affected joints painfulness of joints) and laboratory (red cell sedimentation rate, circulating immunocomplexes) indicators. A favourable effect (improvement of at least five of the above indicators) was recorded in 42.1% of the children. Undesirable effects were found in 11 children (30%) incl. six where they were the cause of discontinuation of treatment. All undesirable effects were reversible. The majority of them (exanthema, headache, leukopenia, microscopic haematuria) developed during the first 3-4 weeks of treatment.