We evaluated the efficacy and safety of naproxen (10-20 mg/kg/d) for the treatment of arthritis and fever related to rheumatic fever in 19 children. Fever and arthritis resolved within a median of 1 day of beginning treatment (range, 1-2 and 1-30 days, respectively). The sole patient with prolonged arthritis had small joint involvement. No gastrointestinal, dermatologic, liver, or renal side effects were observed. None of the patients developed carditis over the following 6 months. Naproxen appears to be effective for the treatment of arthritis and fever related to rheumatic fever and is well tolerated.