BACKGROUND/PURPOSE To provide a framework for clinicians to manage acute pancreatitis, evidence-based guidelines have been developed by the Japanese Society of Abdominal Emergency Medicine. METHODS Evidence was collected by a systematic search of MEDLINE and Japana Centra Revuo Medicina. A total of 1348 papers were reviewed and levels of evidence were assessed. Practical recommendations were also graded. RESULTS The present guidelines consist of introductions, a summary of recommendations, practice algorithms, definitions, epidemiology, diagnosis, severity assessment, and therapy. The main points of recommendation in these guidelines are: (1) measuring lipase for the diagnosis of acute pancreatitis (recommendation grade [RG], A). (2) The Severity of acute pancreatitis should be assessed using a scoring system, such as that of the Japanese Ministry of Health and Welfare or Acute Physiology and Chronic Health Evaluation (APACHE) II (RG, A). (3) Enhanced computed tomography (CT) should be used for assessment of degree of pancreatic necrosis and inflammation (RG, B). (4) Prophylactic antibiotic administration should be used for severe pancreatitis (RG, A), but not for mild to moderate pancreatitis (RG, D). (5) Gabexate mesilate should be used for severe pancreatitis (RG, B). (6) Enteral feeding should be used for all pancreatitis (RG, B). (7) Continuous hemodiafiltration and continuous arterial infusion of proteinase inhibitor and antibiotics may be of benefit (RG, C). (8) Fine-needle aspiration should be done for the diagnosis of infectious pancreatic necrosis, and if positive, necrosectomy is indicated (RG, A). CONCLUSIONS These guidelines provide useful information for physicians to manage this troublesome disease.