Pulmonary disease related to inorganic dust exposure has been recognized for a long time, but it has gained increasing attention from clinicians, pathologists, and other health care professionals in recent years. Certain pathologic reactions, such as dense, rather acellular hyalinized nodules in silicosis, peribronchiolar interstitial fibrosis in asbestosis, and intra-alveolar and interstitial accumulation of anthracotic-laden macrophages in coal workers' pneumoconiosis, are patterns well recognized by pathologists as relating to specific inorganic dust exposure. However, the lung has a limited repertoire of response to injury, and although certain patterns such as noncaseating granulomata in sarcoidosis, diffuse interstitial fibrosis of usual interstitial pneumonitis, accumulation of large numbers of intra-alveolar macrophages in desquamative interstitial pneumonitis and of a peculiar lipoproteinaceous material in pulmonary alveolar proteinosis are largely associated with diseases of unknown origin.