Pretreatment with inhaled beta 2-agonists is often recommended for the prevention of exercise-induced bronchoconstriction. Regular treatment with inhaled beta 2-agonists has been associated with worsened baseline airway caliber and increased airway responsiveness. In this study, we have investigated the effects of regular inhaled albuterol on the severity of exercise-induced bronchoconstriction using a double-blind, placebo-controlled, randomized, crossover design. Ten subjects inhaled either albuterol or placebo (2 x 100 micrograms, four times per day) for 7 d. On the eighth and ninth days of treatment periods, subjects performed 5-min constant work rate cycle ergometry exercise challenges after inhaling 200 micrograms of placebo (eighth day) or albuterol (ninth day). Forced expired volume in 1 s (FEV1) was measured on arrival in the laboratory as well as before and for 1 h after exercise. One week of regular inhaled albuterol compared with placebo resulted in: (1) a lower baseline FEV1 (mean difference, 230 ml) (p = 0.02); (2) a lower minimum postexercises FEV1 without inhaled albuterol pretreatment (mean difference, 390 ml; range, -50 ml to 1,250 ml) (p = 0.01); (3) a lower minimum postexercise FEV1 with inhaled albuterol pretreatment (p < 0.01). The smallest degree of exercise-induced bronchoconstriction occurred after a week of regular placebo and pretreatment with inhaled albuterol immediately before exercise. Inhalation of albuterol four times daily for 1 wk worsens exercise-induced bronchoconstriction; however, it remains extremely effective when used immediately before exercise for preventing bronchoconstriction.