We have recently reported that treatment of patients with severe atopic dermatitis with recombinanl interferon-gamma (rIFN-y) resulted in clinical improvement as well as a reduction of circulating eosinophils. Since IgE-dependent late phase allergic reactions and eosinophilic infiltration are thought to play an important role in the pathogenesis of asthma, we conducted a two centre randomized double-blind placebo-controlled trial of rIFN-y in the treatment of steroid-dependent asthma. Patients were treated with daily subcutaneous injections of either 0.05 mg/m2 rIFN-y (n= 9) or placebo (n=11) for 90 days. All patients completed the study without significant drug toxicity noted. Oral prednisone dose, forced expiratory volume in 1 second (FEV), peak expiratory flow rates (PEFR) and circulating eosinophil counts were monitored throughout the trial. There was no significant difference between the two treatment groups in per cent reduction from baseline of daily prednisone (P=0.51). There was also no significant difference between the two treatment groups in per cent change from baseline in FEV1 (P= 0.54)or in PEFR (P=0.75). Total circulating eosinophil counts decreased by 31% in the rIFN-y group and increased by 8.5% in the placebo group (P= 0.09). We conclude that this treatment regimen was not effective in patients with steroid-dependent asthma.