Seventy-three adult, steroid-dependent asthmatic patients participated in a 16-wk, double-blind study testing the efficacy of flunisolide aerosol. Forty received flunisolide, and 33 received placebo. The mean daily prednisone requirement of patients receiving flunisolide fell 59.2% during the testing period, and that of the patients receiving placebo fell 19.7%. The median daily prednisone dose dropped 74.4% in the flunisolide group and 4.2% in the placebo group (p = 0.006). In the flunisolide group 75% tapered use of oral steroids 50% or more, and 27.5% stopped taking oral steroids completely. In the placebo group 36% tapered use of oral steroids 50% or more, and only 12% stopped taking them completely. Despite their reduction in systemic steroids, those patients receiving flunisolide achieved significantly greater reduction in the daily severity of wheezing (p = 0.014) and frequency of asthma attacks (p = 0.049) than did those receiving placebo. In the final evaluation of therapeutic response, 70% of patients receiving flunisolide were rated as having a very good or good response, and 30% were rated as having a fair or poor response. In contrast 33% of patients receiving placebo were rated as very good or good, and 67% were rated as fair or poor (p = 0.0009). No serious reactions were reported. Plasma cortisols showed an average increase of 42.9% in the flunisolide group but no change in the placebo group. Flunisolide aerosol is a well-tolerated and effective agent in the treatment of steroid-dependent asthma.