The Japanese Guidelines for management of acute cholangitis and cholecystitis were published in 2005 as the first practical guidelines presenting diagnostic and severity assessment criteria for these diseases. After the Japanese version, the Tokyo Guidelines (TG07) were reported in 2007 as the first international practical guidelines. There were some differences between the two guidelines, and some weak points in TG07 were pointed out, such as low sensitivity for diagnosis and the presence of divergence between severity assessment and clinical judgment for acute cholangitis. Therefore, revisions were started to not only make them up to date but also concurrent with the same diagnostic and severity assessment criteria. The Revision Committee for the revision of TG07 (TGRC) performed validation studies of TG07 and new diagnostic and severity assessment criteria of acute cholangitis and cholecystitis. These were retrospective multi-institutional studies that collected cases of acute cholangitis, cholecystitis, and non-inflammatory biliary disease. TGRC held 35 meetings as well as international email exchanges with co-authors abroad and held three International Meetings. Through these efforts, TG13 improved the diagnostic sensitivity for acute cholangitis and cholecystitis, and presented criteria with extremely low false positive rates. Furthermore, severity assessment criteria adapted for clinical use, flowcharts, and many new diagnostic and therapeutic modalities were presented. The worldʼs first management bundles of acute cholangitis and cholecystitis were also presented. The revised Japanese version was published with the same content as TG13. An electronic application of TG13 that can help to diagnose and assess the severity of these diseases using the criteria of TG13 was made for free download.