A 53-year-old woman with a smoking history of 20 pack-years was admitted to the hospital because of dry coughing and exertional dyspnea that had progressed over the previous 3 months. A chest X-ray film taken one month before the onset of symptoms was almost normal. Diffuse small nodular shadows with infiltration were evident one month after the onset of symptoms, and increased rapidly until admission to the hospital. Eosinophilic granuloma was diagnosed histologically after thoracoscopy. The symptoms, chest X-ray findings and pulmonary-function data improved spontaneously after admission to the hospital and the nodular shadows had a almost completely disappeared by 5 months later; the patient continued to smoke. The present case is unique and valuable because it shows the natural course of eosinophilic granuloma from the onset of symptoms to remission.