Twenty-three steroid-dependent severely asthmatic patients, ranging in age from 20 to 67 years, tolerated reduction in their oral dosage of steroids during a one-year trial of triamcinolone acetonide aerosol. Sixteen patients maintained their initial one-second forced expiratory volume without oral therapy with steroids, two required resumption of daily steroid dosage because of lethargy and arthralgia, and four required 2.5 to 20 mg of prednisone every other day to control their asthma. Five-day oral courses of steroids were occasionally required because of episodes of asthma from a variety of external causes. One patient failed to benefit within two months and withdrew from the study. One patient had precipitins to Candida albicans prior to the study, and he developed transient oropharyngeal culture-positive thrush, which subsided with use of a gargle containing nystatin. None of the other patients had oral candidiasis, and laryngoscopic examination revealed no lesions attributed to the aerosol. The mean fasting cortisol level did not increase throughout the one-year trial. Thus, the use of triamcinolone acetonide aerosol (2,000 microgram or less daily) can eliminate or greatly reduce oral requirements for steroids in patients with severe steroid-dependent asthma. Side effects are mild, but adrenal recovery may be exceedingly slow.