Chronic Obstructive Pulmonary Disease (COPD) is a clinical syndrome defined as non- or incompletely reversible airflow obstruction associated with persistent lower respiratory symptoms such as dyspnea, cough, and excessive sputum production. The present definition probably includes more than one disease. Despite being largely preventable, COPD is often a disabling disease with accelerated longitudinal lung function loss and systemic comorbidities and is presently the third leading cause of death and one of the most important health care expenditures worldwide. While most cases are unquestionably related to tobacco smoking, it has long been suspected and is also now fairly well established that occupational and environmental exposures, as well as a variety of other factors, contribute to its causation. Most recent estimates place the fraction of COPD causation by occupational exposures at ~15% and ~30% overall and among nonsmokers, respectively. The disease occurs in workers exposed to vapors, gases, dust, and fumes at their longestheld job, and in several occupations that include miners, agricultural, cotton/textile, and construction workers, food, drink, and tobacco processors, and bus drivers, among others. There is evidence of an additive effect of occupational exposures and cigarette smoking. There is presently no evidence that treatments differ from those in widely accepted guidelines, except for the occupational interventions for primary, secondary, and tertiary prevention discussed throughout this book. This is in large part due to treatment trials having required a fairly heavy smoking history and disregarded patients’ occupations. Improved appraisal of the etiological contribution of occupational exposures should lead to progress towards disease elimination.