Although prevalence of acute coronary syndrome (ACS) in Japan is much less than in Western countries, it steadily increases in these years. More than half of the total death from ACS are estimated to be a prehospital death due to out-of-hospital cardiac arrest. However, in-hospital mortality has been decreased during these 20 years, mainly due to the progress in reperfusion treatment at emergency care and intensive pharmacological treatment. Regional registration study(OACIS) shows that majority of the patients with ACS are transferred to CCU/ER and treated with primary PCI. Recently, use of drug eluting stent is increasing for treatment of ACS, yielding the good outcome after discharge. Further decrease in mortality is expected with the progress in ACS management technique.