The efficacy and toleration of a new beta1-selective beta-blocker, H 87/07, was compared with placebo in 33 patients with angina pectoris. The efficacy was evaluated using subjective assessments of attack rate and nitroglycerin consumption as well as objective assessments of exercise tolerance on a bicycle ergometer. H 87/07 significantly reduced the attack rate and the nitroglycerin consumption compared with placebo. The mean reduction amounted to 13 and 36% respectively. No significant differences were found between H 87/07 and placebo with regard to exercise tolerance. Due to high intrinsic stimulating activity (I.S.A.) H 87/07 altered the heart rate and blood pressure only slightly at rest but during exercise significant reductions were seen. Except for one patient who had cardiac decompensation on H 87/07 no side-effects of clinical importance were seen. No significant changes were seen with regard to the laboratory tests performed.