Twenty-one asthmatic patients participated in a single blind, crossover study comparing the effects of aerosol and oral salbutamol (a beta-adrenergic bronchodilator), on exercise-induced bronchospasm. By both routes of administration, salbutamol (albuterol) produced significant bronchodilatation at rest, but only the aerosol effectively prevented post-exercise bronchospasm in most patients. Because exercise-induced bronchospasm is a common problem in children and adults with asthma, these observations are relevant to the drug therapy of these patients. The existence of separate mechanisms for bronchodilatation and the prevention of exercise-induced asthma is postulated. It is possible that differing tissue concentrations of salbutamol are responsible for the observed differences between the 2 routes of administration.