Twice-daily and four-times daily treatment with beclomethasone dipropionate aerosol were compared in a double dummy crossover study in patients with severe chronic bronchial asthma. The trial consisted of two two-month treatment periods preceded by a two-week baseline period. No significant difference was found in the morning or evening PEF, in symptom scores for wheeze, cough, sputum, sleep disturbance, limitation of daily activity, rhinitis, daily usage of bronchodilator aerosol or requirement for additional oral corticosteroids. The study has confirmed that in management of severe bronchial asthma, a twice-daily regimen of beclomethasone dipropionate aerosol is as effective as four-times daily treatment, if the total daily dose of beclomethasone dipropionate is kept unchanged.