The adrenal function of children with near fatal asthma was evaluated by a modified rapid ACTH test. The rapid ACTH tests, which were performed within six months of each life-threatening asthmatic episode, showed extremely low responsiveness. The response in the subjects was significantly lower than that of patients who had received high dose of corticosteroid therapy. It was suggested that the adrenocortical function of children with near fatal asthma had been already suppressed and that adrenal suppression could easily occur in such patients. We advocate the following measures: (1) environmental control, education of patients and their families, physical training accurate medication should be supplied to reduce the use of corticosteroids, (2) sufficient doses of corticosteroids should, however be given to patients with acute exacerbation, (3) not only lung function tests or allergic examinations, but also adrenocortical function tests should be performed on severe asthmatic patients.