Leflunomide is a low-molecular weight, synthetic, oral agent specifically developed for immunosuppression. Because of activity in animal models, leflunomide was tested in rheumatoid arthritis(RA). These investigations have demonstrated that leflunomide reduces the clinical symptoms and signs of RA, improves health related quality of life, and retards structural damage. Leflunomide has been evaluated in RA patients as monotherapy and in combination with methotrexate. Close monitoring for adverse events with particular attention for monitoring liver enzymes for hepatic toxicity is important during treatment with leflunomide.