Occupational and environmental carcinogens account for an important minority of cases of bronchogenic carcinoma. From a public health perspective, it is important to characterize occupational and environmental carcinogens and to define disease risk to reduce preventable lung cancer. From a clinician's perspective, it is important to distinguish individual cases of occupational lung cancer from nonoccupational cases, because cancer acquired from work may be compensable through worker's compensation claims and litigation. Important carcinogens include asbestos, radon daughters, diesel exhaust, and metals. Epidemiologic investigations identify excess cases of lung cancer in populations exposed to carcinogens. Experimental animal and ex vivo human research provide complementary information supporting causal relationships between exposure and carcinogenesis. Clinical challenges include proving that a given case of lung cancer is due to an occupational exposure. Research challenges include determining safe exposure thresholds. Only a small percentage of all chemicals used in industry have been extensively analyzed for their carcinogenic potential. Scientific and regulatory information about pulmonary occupational and environmental health and safety is available from several important agencies and organizations, including the Occupational Safety and Health Administration, the National Institute for Occupational Safety and Health, the International Agency for Research on Cancer, the American Lung Association, and the Environmental Protection Agency.