FACTORS. Chronic Obstructive Pulmonary Disease (COPD) is a very important cause of morbidity and mortality in industrialized and developing countries. According to the World Health Organization (WHO), in 2020 COPD will become the third leading cause of death all over the world. To date, several risk factors for developing COPD have been studied. They can act either singly or interacting among themselves in a synergistic way. Smoking habits and aging are the most important factor for development and exacerbation of COPD, but environmental conditions, such as air pollution and work exposure, can be relevant factors. Recommendations for the prevention of COPD, beside the promotion of smoking cessation, may be air pollution abatement and control of professional exposure. In view of historical trend of risk factors exposure, further epidemiological studies are necessary for a better knowledge of COPD natural history.