The effect of inhaled beclomethasone dipropionate (dose, 400 mug daily) was investigated in 31 prednisone-dependent asthmatics. In a double-blind noncrossover study of 25 patients dependent on a daily prednisone dose of 17.5 mg or less, the dose of ingested prednisone was significantly diminished through the use of beclomethasone as compared with placebo (P < 0.001). In a subsequent single-blind study of the 12 patients who had received placebo, a similar decrease in prednisone dose was possible when these patients received beclomethasone. In all 25 patients the effect of beclomethasone was maintained for 2 years; 9 came to require less beclomethasone and 1 required more. In an additional single-blind study of six patients with severe asthma, dependent on prednisone in a dose of 20 to 25 mg/d, the response to beclomethasone was more variable and less significant (P < 0.01). However, at 2 years there was no significant benefit (P > 0.05) and there were two treatment failures.In patients in whom reduction of dose or discontinuation of prednisone was possible plasma cortisol values before and after corticotropin administration increased significantly (P < 0.001). Prednisone reduction was associated with the appearance of mild musculoskeletal steroid-withdrawal symptoms of short duration in 15 patients, and recurrence of symptoms of rhinitis in 15 patients. Side effects of beclomethasone included episodes of hoarseness in 6 and easily treated oropharyngeal Candida albicans infection in 14.