A 56-year-old woman was referred to our hospital because of dyspnea, wheezing, and a productive cough. Eight years before presentation, bronchial asthma was diagnosed and the patient received inhaled corticosteroids plus antiasthmatic agents (a long-acting inhaled beta2-agonist, leukotriene modifiers, and theophylline). Chest radiography showed small diffuse nodular shadows, and a computed tomographic scan showed thickening of the bronchi and bronchioles, with diffuse centrilobular nodules in both lung fields. A blood test and microscopic examination of the bronchoalveolar fluid revealed marked eosinophilia. Transbronchial lung biopsy and transbronchial biopsy showed eosinophilic bronchitis and bronchiolitis. After treatment with oral prednisolone (40 mg daily) and inhaled corticosteroids, the symptoms, blood eosinophilia, and radiographic findings improved. Recently, several similar cases of eosinophilic bronchiolitis have been reported. Studies of further cases and elucidation of the pathophysiology of eosinophilic bronchiolitis are necessary to establish a concept for this disease and to determine whether it should be classified as a subtype of bronchial asthma or as a distinct entity.