During a seven-year interval, 78 children had documented episodes of respiratory failure from asthma, defined as arterial hypoxemia, hypercapnia, or use of mechanical ventilatory support or intravenous isoproterenol hydrochloride. During 407 patient-years of follow-up (5.2 years per patient), these 78 children had 227 episodes of respiratory failure (2.9 episodes per patient). Fifty-three patients (68%) have had two or more of such episodes. Second episodes usually followed the initial episodes within two years, but some were delayed for over six years. Seven of the 78 children died, and two others have incurred hypoxic brain damage, compared with two deaths among 2892 children with asthma--seen at this hospital during that interval--but without a documented previous episode of respiratory failure. We conclude that children whose asthma has caused even one episode of respiratory failure constitute a special group of asthmatic patients, members of which are at high risk for repeated episodes of respiratory failure and its catastrophic complications. This recognition allows special attention to be focused on them in designing both clinical and research strategies.