Chronic obstructive pulmonary disease (COPD) refers to a group of disorders characterized by a persistent reduction in the maximal rate of exhalation despite aggressive treatment. In the United States, COPD was ranked as the fifth leading cause of death in 1989, and mortality rates are increasing, especially among women.¹ The conditions best recognized as causing COPD — chronic bronchitis and emphysema — most often result from cigarette smoking and are typically coincident. Asthma also causes COPD; severe, irreversible airflow obstruction is found in some patients with a long history of asthma and no other identifiable risk factors.² Indeed, evidence that . . .