Intraaortic balloon pump support has been demonstrated to be of clinical benefit when used therapeutically and prophylactically in high-risk patients undergoing percutaneous transluminal coronary angioplasty (PTCA). Afterload reduction and post-PTCA-enhanced coronary blood flow afforded by diastolic augmentation during intraaortic balloon pumping provides hemodynamic stabilization, attenuates clinical perturbations of myocardial ischemia, and may provide an important 'bridge' to emergent coronary bypass surgery following abrupt vessel closure complicating PTCA. Recent studies demonstrate a reduction in cardiac morbidity and improved coronary artery patency among patients receiving prophylactic intraaortic balloon pumping after establishing infarct artery reperfusion during acute cardiac catheterization for acute myocardial infarction. A modest increase in cardiac output (20-30%), the requirement of a stable, regular cardiac rhythm, peripheral vascular disease and aortic insufficiency limits the use of intraaortic balloon pump support in relatively few patients. These studies demonstrate that intraaortic balloon counterpulsation provides an effective and safe form of mechanical support in many high-risk patients undergoing PTCA.