Abstract In a double-blind crossover study of 18 hypertensive asthmatic patients, an isoproterenol aerosol caused a drop in diastolic pressure and an elevation of the pulse rate 2 and 5 minutes after its use. A combination isoproterenol-phenylephrine aerosol caused no significant changes in pulse or blood pressure. Pulmonary function studies showed substantial but statistically equal improvement 10 minutes after the use of the two aerosols. Placebos were ineffective. Twelve of the patients preferred the combination aerosol or could tell no differences between the two. Side effects were minimal. The isoproterenol-phenylephrine aerosol appears to be safe to use in the presence of uncomplicated hypertension.