Context .- Emphysema, respiratory bronchiolitis, desquamative interstitial pneumonia, pulmonary Langerhans' cell histiocytosis, small-airway injury including submucosal and adventitial fibrosis, increased bronchus-associated lymphoid tissue, and small artery/arteriolar wall thickening are recognized histologic findings in cigarette smokers. It has only recently been acknowledged that the range of lung injury from cigarette smoke is wider than generally accepted, in particular, there is increasing recognition that fibrosis of alveolar walls occurs in smokers. Objectives .- To review the literature that describes the range of histologic findings in cigarette smokers and that links cigarette smoke exposure to the development of alveolar wall fibrosis. Data Sources .- Relevant peer-reviewed literature indexed in PubMed (National Library of Medicine) form the basis of this review. Conclusions .- Smokers demonstrate a wide range of lung injury at biopsy that defies simple placement within single categories, and the current categories do not adequately take into account the importance of alveolar wall and airway fibrosis.