The most common adverse events reported with the use of leflunomide are hypertension, infections, alopecia, and various gastrointestinal complaints. No fatal adverse hematologic events have been reported in humans, although anemia and leukopenia have been described in animals receiving 20 mg/kg/day. We describe a patient with relapsing polychondritis, in whom treatment failure with glucocorticoids, methotrexate, hydroxychloroquine, and azathioprine led to the institution of therapy with leflunomide at a maintenance dose of 20 mg/day. Two months after the dose of leflunomide had been increased to 30 mg daily, the patient developed high fevers, photophobia, thrombocytosis, and leukocytosis that returned to normal following treatment with cholestyramine and discontinuation of leflunomide. Rechallenge with leflunomide was not attempted and the syndrome did not recur during 14 month followup.