The clinical effectiveness of albuterol, isoetharine, and metaproterenol administered by aerosol inhalation at manufacturer-recommended doses was compared. A double-blind, placebo-controlled, crossover comparison of albuterol 280 micrograms, isoetharine 680 micrograms, and metaproterenol 1300 micrograms was conducted in 10 adult men with reversible, chronic pulmonary obstruction. FEV1 (forced expiratory volume at one second), FEF25-75 (forced expiratory flow rate from 25 to 75% of vital capacity), and FVC (forced vital capacity) were determined periodically for six hours after drug administration. Bronchodilator effects, adverse effects, and cost of treatments were compared. Theophylline therapy was unaltered during the study, and serum theophylline concentration was determined periodically to control for its effect on pulmonary function. Serum theophylline concentration was not used as a covariate since it resulted in minimal change in the pulmonary-function measures. The mean maximum percent change from baseline for FEV1 for each drug was superior to placebo; there were no differences among drugs. Comparing area under the curve of mean percent change in FEV1 versus time, albuterol and metaproterenol produced changes that were greater than placebo but not different from each other or isoetharine. For FEF25-75 and FVC, albuterol and metaproterenol, respectively, were superior. No pattern of adverse effects was identifiable among the four treatments. The average wholesale cost of albuterol products was approximately 1.7 times the cost of metaproterenol products. Under the conditions of this study, metaproterenol was superior to isoetharine and therapeutically equivalent to and less expensive than albuterol.