Altogether 212 patients aged 16 to 73 years with rheumatoid arthritis (RA) lasting 3 months to 32 years were examined. Of these, 78 patients had grade I, 111 grade II, and 23 grade III disease activity. 34 patients had stage I, 76--stage II, 56--stage III, and 24--stage IV disease. In 22 patients, roentgenography failed to reveal pathology of the joints. The reference group comprised 65 patients suffering from gouty arthritis, 46 having osteoarthrosis deformans with phenomena of secondary synovitis, 30 with Bekhterev's disease, 10 with systemic lupus erythematosus, 6 with Reiter's disease, 5 with psoriatic arthropathy, and 50 with non-rheumatic diseases. When trying the diagnostic criteria for ARA (revised in 1987), criteria 1-4 and 7 were found to be most sensitive (from 88.2 to 93.8%), criteria 5 and 6 appeared most specific (100 and 98.6%, respectively). The specificity of the remaining criteria ranged from 85.4 to 96.3%. The use of the revised criteria for ARA in clinical practice was dictated by the necessity of improving RA diagnosis.