Use of racemic epinephrine hydrochloride (Vaponefrin), delivered by intermittent positive-pressure breathing, in the treatment of laryngotracheobronchitis (croup) produced acute beneficial results in a controlled study. However, symptoms often recurred within two hours, suggesting that this form of treatment should not be used in the emergency room and the patient then sent home. This treatment had no effect on arterial oxygen gas pressure. The changes in clinical status 24 to 36 hours after admission into the study were similar for the patients in the treatment and control groups, suggesting that the natural history of the disease was not drastically altered by this form of treatment.