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 .mu.g, isoetharine 680 .mu.g and metaproterenol 1300 .mu.g was conducted in 10 adult men with reversible, chronic pulmonary obstruction. FEV1 (forced expiratory vol at 1 s), FEF25-75 (forced expiratory flow rate from 25-75% of vital capacity) and FVC (forced vital capacity) were determined periodically for 6 h after drug administration. Bronchodilator effects and adverse effects 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 vs. 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 4 treatments. Under these conditions, metaproterenol was superior to isoetharine and therapeutically equivalent to albuterol.