The administration of systemic corticosteroids for patients with exacerbations of chronic obstructive pulmonary disease (COPD) has become common practice over the past 25 years. This practice remained somewhat controversial because corticosteroids can have serious adverse effects and initial clinical trials provided inconclusive evidence concerning their efficacy. Results from recent clinical trials indicate that systemic corticosteroids are modestly effective in shortening the duration of severe exacerbations of COPD. Systemic corticosteroids administered intravenously or orally to hospitalized patients with exacerbations of COPD reduced the absolute treatment failure rate by about 10%, increased the forced expiratory volume in 1 second (FEV1) by about 100 ml, and shortened the hospital stay by 1 to 2 days. Oral corticosteroids probably confer similar benefits when used for treating moderately severe COPD exacerbations in an out-patient setting. The optimal starting dose of corticosteroids is not known, but the duration of treatment should not extend longer than 2 weeks. Hyperglycemia is the most common adverse event, but secondary infections, mental disturbances, and myopathies may also occur.