Ten patients with life-threatening attacks of asthma (status asthmatiucus') were treated with salbutamol inhaled by intermittent positive pressure breathing, and their response in terms of rise in peak flow rate was measured. They were then given intravenous salbutamol and any further increment in peak flow was measured. Hydrocortisone treatment was started simultaneously and the responses to salbutamol were re-measured on each of the next three days. Only two patients initially responded to the aerosol, whereas all save one responded to the intravenous drug. The two who responded initially to the aerosol were the two who were able to produce sputum at the time of admission. All patients subsequently responded to the aerosol, and the onset of this response correlated closely with the beginning of sputum production. Sympathominetics should be given parenterally to patients in severe asthma if the response to inhaled drug is reduced or absent.