To evaluate the role of corticosteroids as treatment for acute exacerbations of chronic obstructive pulmonary disease, we conducted a double-blind, randomized, placebo-controlled trial in 44 consecutive patients with chronic bronchitis and severe airflow obstruction. All were hospitalized with acute respiratory insufficiency from acute bronchitis. Patients with asthma, atopy, or pneumonia were excluded. Treatment consisted of intravenous aminophylline, inhaled isoproterenol, antibiotics, and either methylprednisolone, 0.5 mg/kg of body weight, or placebo every 6 h intravenously for 72 h. Bedside spirometry was done before and after bronchodilator inhalation three times daily. The methylprednisolone-treated group had a greater improvement in both prebronchodilator and postbronchodilator forced expiratory volume in 1 second (P less than 0.001). More patients with large improvements in their prebronchodilator or postbronchodilator flow rates, or both (greater than or equal to 40% by 72 h), received methylprednisolone (P less than 0.01). Methylprednisolone improved airflow more than placebo when added to standard therapy in patients with chronic bronchitis and acute respiratory insufficiency.