52 severely ill asthmatic patients requiring acute admission to hospital entered a double-blind placebo-controlled trial to determine whether intravenous hydrocortisone given in addition to high-dose oral prednisolone and standard bronchodilator therapy accelerated recovery. Patients who had been given parenteral steroids before admission, by comparison with those who had not received such treatment, had been deteriorating for a shorter period before admission, had received more injected or nebulised bronchodilator therapy, and had higher admission peak flows. As judged by peak flow measurements 24 h after admission, parenteral steroids had no effect on the outcome, irrespective of whether they were given before or after (ie, intravenous hydrocortisone) admission. There is no evidence for the continued use of intravenous hydrocortisone in addition to oral prednisolone and bronchodilator therapy in patients admitted to hospital with severe asthma without ventilatory failure.