Leflunomide is a member of the disease modifying anti-rheumatic drugs group used as a treatment modality in active rheumatoid and psoriatic arthritis. "Oral ulcers" are reported in 3-5% of leflunomide medicated rheumatoid arthritis patients with adverse events, but they are not described in detail in the literature. We present a case of an ulcer in the tongue of a rheumatoid arthritis patient managed with leflunomide and contemplate on its pathogenesis. Key words:Leflunomide, oral ulcer, DHODH.