Pulmonary infiltrates developed in three middle-aged women while receiving naproxen sodium. Weakness, fatigue, cough, low-grade fever, and eosinophilia in blood and/or sputum were common to all. All symptoms and findings resolved within a few days after discontinuing naproxen therapy in two cases and with use of corticosteroids (prednisone) in one case. A hypersensitivity reaction due to naproxen seemed to be the likely cause.