Aim To compare the effectiveness and safety of leflunomide(LEF) with those of methotrexate(MTX) in patients with active rheumatoid arthritis(RA). Methods 95 RA patients were randomly assigned to receive LEF or MTX. The patients in the treated group received LEF 20 mg·d -1 and in the controlled group who received MTX 15 mg/wk totally 12 weeks. Results The total effective rates of the treated group and the controlled group were 90.0 %(n =50 ) and 95.6 %(n =45 ) respectively. There was no statistical significance between the two groups in the effectiveness (P0.05).The adverse reaction rate was 14.0% (7 case) in the treated group and 15.6%(7 cases) in the controlled group. There was no significance difference between the two groups (P=0.83). But the adverse reactions were more tolerable in LEF group than in MTX group. Conclusion This study suggests that LEF is an effective and more safe drug for active rheumatoid arthritis in our country.