The effect of chronic oral therapy with acebutolol, a cardioselective beta adrenergic blocking agent, was evaluated on resting pulmonary functions in a group of patients who were free of overt obstructive airways disease and who had chronic stable angina pectoris. The study design involved a 20-week, placebo-controlled, double-blind, randomized cross-over trial, using acebutolol, an agent with partial agonist activity that has been shown to be effective in the treatment of hypertension, cardiac arrhythmias, and angina pectoris. Utilizing spirometry, flow volume loops, and arterial blood gas analyses, this study demonstrated that acebutolol had no significant deleterious effect on resting pulmonary function when used in clinically effective dosages.