Heart rates (HR) were measured before (control HR) and after (ischemic HR) balloon inflation during percutaneous transluminal coronary angioplasty in 96 patients with effort angina pectoris. The delta HR, defined as (ischemic HR-control HR), in the right coronary artery occlusion was significantly smaller than that in the left anterior descending artery or left circumflex artery occlusion. Among right coronary artery occlusions the delta HR in segment 1 occlusion was significantly smaller than that in segment 2 or segment 3 occlusion. It is suggested that the ischemia of the right ventricle plays an important role in producing a reflex bradycardic response in humans.