We evaluated the effect of betaxolol on the pulmonary function tests of nine patients with glaucoma and chronic obstructive pulmonary disease (COPD) requiring beta-blocker therapy. The results of pre-treatment pulmonary function tests were compared to results after two weeks of betaxolol therapy. The mean ratio of forced expiratory volume in one second (FEV-1) to forced vital capacity (FVC) was 59.33 +/- 13.30%. After two weeks of betaxolol therapy, the resulting mean FEV-1/FVC was 57.89 +/- 13.89%, a statistically insignificant difference (P greater than 0.05). The mean FEV-1 was 1.94 +/- 0.83 liters, compared to 1.91 +/- 0.78 liters after two weeks of betaxolol. The mean FVC was 3.19 +/- 0.91 liters, compared to 3.23 +/- 0.89 liters after two weeks of betaxolol. These differences were, also, not statistically significant (P greater than 0.05). This prospective study supports previous reports suggesting that betaxolol has potential advantages for those patients at risk for developing pulmonary side effects from beta-blocker therapy. This report represents the largest single-center series of patients who have been studied in this fashion.