OBJECTIVE: To report a case of skin ulceration as a result of treatment with leflunomide for rheumatoid arthritis. CASE SUMMARY: A 78-year-old white woman developed bilateral leg ulcers after 6 months of treatment with leflunomide for rheumatoid arthritis. A history of leg ulcers after methotrexate therapy had been documented. Serologic and diagnostic tests did not support an alternate process. Other medications prescribed were oral ethinyl estradiol 0.05 mg/d, felodipine 5 mg/d, and paroxetine 20 mg/d, for which no documented correlation with the skin breakdown could be made. DISCUSSION: This is the first published case describing a possible relationship between the use of the immunosuppressant agent leflunomide and skin ulceration. CONCLUSIONS: Skin breakdown and ulceration is a recognized adverse effect of drugs with immunosuppressant activity such as methotrexate. Leflunomide, a newer agent prescribed in the treatment of rheumatoid arthritis, may now be listed among the drugs in this category associated with this adverse drug effect.