The coexistence of coronary artery disease (CAD) and chronic obstructive pulmonary disease (COPD) is frequent because of common etiological factors. Beta-blockers remain underutilized in patients with CAD who also have COPD. This study was performed to evaluate the safety of beta-1 selective blocker agents in CAD patients with COPD. Fifty patients (aged 57.3 +/- 10.1 years) were enrolled in this study; 27 patients received metoprolol CR (controlled release), and 23 received metoprolol (conventional). The patients were stratified according to the severity of COPD (21 severe, 21 moderate, and 8 mild), started on metoprolol CR or conventional metoprolol, and titrated up to the maximum tolerated dose. The clinical controls were done during the first week and then at the first and third month. Patients received a mean total daily dose of 92.5 +/- 18 mg of metoprolol CR or 189 +/- 36.7 mg of metoprolol. Seven patients could not receive the maximum dose. There was no significant decrease in forced expiratory volume in 1 s (FEV(1)) in either group (basal vs last FEV(1): 54.5% +/- 13.4% vs 54.3% +/- 13% in the metoprolol CR group and 49.6% +/- 14.5% vs 53.2% +/- 12.8% in the metoprolol group). No adverse event was experienced. Metoprolol, a beta-1 selective blocker, can be used safely at the maximum dose in CAD patients with COPD.