The relationships between cigarette smoking and heart disease, lung cancer, and chronic obstructive pulmonary disease (COPD) are well known; in contrast, the topic of the relationship between smoking and interstitial lung disease is almost obscure. Despite its lack of a public persona, this relationship is important, since smoking plays a key role in the pathobiology of several interstitial lung diseases — respiratory bronchiolitis, desquamative interstitial pneumonia, pulmonary Langerhans'-cell histiocytosis, and perhaps idiopathic pulmonary fibrosis ...