To investigate the effect of beta 2-agonists on exercise performance, eight asthmatics performed an incremental exercise test on a treadmill. Five minutes before the start of the exercise, they were treated with inhaled salbutamol or placebo in a double-blind manner. The exercise started at a low intensity (2 mph, 10% inclination), and every 3 min the speed was increased by 0.5 mph at the same inclination until the subjects were exhausted. Every minute peak expiratory flow, heart rate, blood lactate concentration, and rating of perceived exertion were measured. The same parameters were also measured following the completion of the exercise. No significant difference was seen in total working time, maximal lactate concentration, heart rate, or rating of perceived exertion, whereas the decrease in peak expiratory flow was reduced following pretreatment with salbutamol. It is concluded that the release of inhaled beta 2-agonists for use in competitive events is justified as no ergogenic effect was seen.