The intraaortic balloon pumping (IABP) is the most widely used circulatory assist device. IABP increases coronary perfusion in diastolic phase by the inflation of the balloon in the descending aorta (diastolic augmentation) and reduces afterload in systolic phase by the deflation of the balloon( systolic unloading). IABP improves the hemodynamic condition of patients who fall into acute heart failure and/or cardiogenic shock. Six-type IABP system can be used in Japan. The IABP-SHOCK II trial shows that there is no significant difference in mortality between optimal medical treatment with IABP and without IABP in addition to early revascularization. Clinical backgrounds in Japan are different from those in IABP-SHOCK II trial, and the further prospective studies of IABP in Japan thus called for.