Treatment of acute pancreatitis(AP) is one of the critical challenges to the field of gastroenterology because of its high mortality rate and high medical costs associated with the treatment of severe cases. Early-phase treatments for AP have been optimized in Japan, and clinical guidelines have been provided. However, changes in early-phase treatments and the relationship between treatment strategy and clinical outcome remain unclear. Retrospective analysis of nationwide epidemiological data shows that time for AP diagnosis has shortened, and the amount of initial fluid resuscitation has increased over time, indicating the compliance with guidelines. In contrast, prophylactic use of broad-spectrum antibiotics has emerged. Despite the potential benefits of early enteral nutrition, its use is still limited. The roles of continuous regional arterial infusion in the improvement of prognosis and the prevention of late complications are uncertain. Furthermore, early-phase treatments have had little impact on late-phase complications, such as walledoff necrosis, surgery requirements and late(> 4 w) AP-related death. Based on these observations, earlyphase treatments for AP in Japan have approached the optimal level, but late-phase complications have become concerning issues. Early-phase treatments and the therapeutic strategy for late-phase complications both need to be optimized based on firm clinical evidence and cost-effectiveness. Treatment of acute pancreatitis (AP) is one of the critical challenges to the field of gastroenterology because of its high mortality rate and high medical costs associated with the treatment of severe cases. Early-phase treatments for AP have been optimized in Japan, and clinical guidelines, have been provided. However, changes in early-phase treatments and the relationship between treatment strategy and clinical outcome remain unclear. Retrospective analysis of nationwide epidemiological data shows that time for AP diagnosis has shortened, and the amount of initial fluid resuscitation has increased over in contrast, prophylactic use of broad-spectrum antibiotics has emerged. Despite the potential benefits of early enteral nutrition, its use is still limited. The roles of continuous regional arterial infusion in the improvement of prognosis and the prevention of late complications are uncertain Based on these observations, earlyphase treatments for AP in Japan have approached the optimal level, but late-phase complications, such as walledoff necrosis, surgery requirements and late (> 4 weeks) AP-related death. have become concerned with issues. Early-phase treatments and the therapeutic strategy for late-phase complications both need to be optimized based on firm clinical evidence and cost-effectiveness.