A 4-week single-blind study is reported which compares the responses of 10 matched pairs of adult asthmatic patients to Beclomethasone Dipropionate and Dexamethasone Isonicotinate aerosols, each at 12 metered-doses per day. 2) Therapeutic efficacy was evaluated by measurement of pulmonary function (PEFR) and by a physician's "overall evaluation" scale. 3) Side-effects related to systemic absorption were evaluated by A.M. blood cortisol levels and total eosinophil counts. 4) At the doses studied, Beclomethasone Dipropionate produced both no side-effects and a significant favourable clinical response, while Dexamethasone Isonicotinate produced significant side-effects and a lesser clinical response.