Bronchiolar disorders can be divided into 2 general categories: (1) airway disorders (cellular bronchiolitis and obliterative bronchiolitis) and (2) parenchymal disorders (respiratory bronchiolitis-interstitial lung disease, which occurs in smokers and is treatable with smoking cessation or corticosteroid therapy, and bronchiolitis obliterans organizing pneumonia, an inflammatory lung disease simultaneously involving the terminal bronchioles and alveoli). This article reviews the clinical findings and therapeutic management of bronchiolitis obliterans organizing pneumonia.