The applicants propose to recruit patients with COPD from patients admitted to hospitals for treatment of COPD, established pulmonary practices in major teaching hospitals, and an associated large health care provider network. Strategies for recruitment include the use of several large clinical databases that have identified patients with COPD. The scientific focus of the proposal is on the prevention and treatment of exacerbations. Exacerbations of COPD, defined as an increase in shortness of breath and an increase in the amount and/or purulence of sputum, are a major determinant of patient quality of life and account for substantial health care expenditures. The applicants propose 2 protocols for consideration by the network; one is directed at treatment of acute exacerbations with inhaled corticosteroids and the second at prevention of exacerbations by use of a leukotriene inhibitor.