This study examined the effects of beta blockade with betaxolol, a cardioselective, lipid-soluble, beta-adrenergic-blocking agent, on rest and exercise systolic and diastolic left ventricular function in 15 patients, aged 40 to 70 years (mean = 52), with chronic stable angina pectoris. Each patient underwent three upright exercise studies at identical workloads; the first was a baseline study, the second was done 3 hours after a single oral dose, and the third was obtained after chronic therapy for 2 weeks. Beta blockade was evident by significant decreases in heart rate, systolic blood pressure, and diastolic blood pressure at rest and during exercise (p < 0.04). Although there were no significant changes (at rest or during exercise) in mean left ventricular ejection fraction and peak filling rate, individual variations were seen after 3 hours and 2 weeks of therapy. During chronic therapy, the peak filling rate increased in three patients, decreased in five, and remained unchanged in seven. Also, discordant changes in systolic and diastolic functions were seen at rest and during exercise during both acute and chronic therapy. Thus, although acute and chronic beta blockade produces no significant changes in mean measurements of diastolic and systolic left ventricular performance, individual variations and discordant results are seen in many patients. The acute effects are generally consistent with the chronic effects, but exceptions are present. © 1987.