Impairment of vagal heart rate control is common in coronary artery disease. To evaluate whether percutaneous transluminal coronary angioplasty (PTCA) has any beneficial effect on this impairment we measured heart rate responses to deep breathing and to standing up, standard tests of cardiac parasympathetic activity, in 28 patients before and 4 weeks after successful PTCA. Before PTCA, 10 patients (36%) had an abnormal heart rate response to deep breathing and one patient (4%) an abnormal response to standing up. The heart rate responses did not change significantly from the preoperative values after PTCA. Thus, the relief of critical coronary obstruction by PTCA seems to have no beneficial effect on vagal heart rate control.