One hundred and ninety one patients with rheumatoid arthritis were included in an open prospective trial with the aim of evaluating the acceptability, efficacy and therapeutic maintenance levels of methotrexate. The mean treatment duration was 19 +/- 13.2 (3-58) months and the mean weekly dose of methotrexate 10.2 +/- 0.2 mg. Analysis of the 191 patients by intention to treat showed a statistically significant improvement in all clinical parameters as well as a significant fall in sedimentation rate with a corticosteroid-sparing effect. The therapeutic maintenance level of methotrexate was 73% at one year, 65% at 2 years and 46% at 5 years. Adverse reactions occurred in 71 patients (37.1%) including 30 who stopped methotrexate permanently as a result. With cautious and strict patient selection, methotrexate could be used in RA as basic treatment of first choice.