A group of adults with 76 episodes of acute asthma needing emergency therapy, but not requiring hospitalization, were discharged from an emergency department following standardized therapy with bronchodilators. Upon discharge, the patients were treated with a controlled regimen of oral theophylline, and were randomly assigned in double-blind manner to either a placebo treatment (42 patient episodes) or a corticosteroid treatment group (34 patient episodes). The latter were given an intravenous bolus of methylprednisolone followed by an eight-day tapering course of oral methylprednisolone, starting at 32 mg twice a day. Follow-up was carried out seven or 10 days after treatment in the emergency department. Relapse could not be predicted on the basis of peak expiratory flow rates measured during care in the emergency department. Those patients who received corticosteroids had a decrease in the need for repeated emergency care (5.9 percent versus 21 percent for placebo) and fewer respiratory symptoms (15.6 percent versus 36.4 percent for placebo). It is concluded that a short course of high-dose corticosteroids in outpatients reduces the relapse rate and symptoms following an acute asthmatic attack.