One hundred and ninety-one patients with severe rheumatoid arthritis (RA) were included in a prospective open longterm study of the safety, efficacy and maintenance of methotrexate (MTX) treatment. The mean duration of MTX treatment was 19 +/- 13.2 (3-58) months; the mean weekly dose of MTX was 10.2 +/- 0.2 mg. Analysis of the 191 patients in an intent-to-treat manner showed a significant improvement of all the clinical variables and a decrease of erythrocyte sedimentation rate with a steroid sparing effect. The probability of continuing MTX therapy for up to 2 years was 65% and for up to 5 years was 46%. Adverse effects of MTX occurred in 37.1% of the patients, but only 15.7% discontinued MTX permanently.