Effects of long-term treatment with pindolol (10 mg twice daily) and metoprolol (100 mg twice daily) on lung function and blood pressure were investigated in eight patients with chronic obstructive lung disease and hypertension. After a placebo period, both beta-adrenoceptor blockers were administered double-blind and cross-over for 4 weeks. By assessing parameters of expiratory flow an attempt was made to distinguish between large and small airways function. Diastolic blood pressure decreased significantly during both pindolol and metoprolol (P less than 0.01). Except for a decrease in forced expiratory volume in 1 s (FEV1) during metoprolol treatment, there was no other change in expiratory flow parameters after placebo or both beta-adrenoceptor blockers. Inhalation of terbutaline induced a small improvement in large airways function after placebo and metoprolol, but not after pindolol; there was no effect of terbutaline on parameters of small airways function. If a beta-adrenoceptor blocker is necessary in patients with chronic obstructive lung disease, a beta 1-adrenoceptor selective blocker is preferred in combination with bronchodilator agents.