IgG4-related disease (IgG4-RD) is a fascinating clinical entity first reported in this century in Japan, and includes a wide variety of diseases, such as formerly named Mikulicz's disease (MD), autoimmune pancreatitis (AIP), interstitial nephritis, prostatitis and retroperitoneal fibrosis. The Japanese IgG4 team organized by the Ministry of Health, Labor and Welfare (MHLW) of Japan has published the first criteria, comprehensive diagnostic (CD) criteria for IgG-RD 2011. Thereafter, IgG4-RD has been accepted widely and many cases have been reported from all over the world. Several problems have arisen in clinical practice, however, including the difficulty obtaining biopsy samples, and the sensitivity and specificity in cut off level of serum IgG4 and impaired immunostaining of IgG4. Given these situations, the Japanese IgG4 team has updated the 2011 comprehensive diagnostic criteria for IgG4-RD and propose the 2020 revised comprehensive diagnostic (RCD) criteria for IgG4-RD, which consists of 3 domains; 1) Clinical and radiological features, 2) Serological diagnosis and 3) Pathological diagnosis. In addition, the new pathological diagnosis is composed by three sub-items including storiform fibrosis and obliterative phlebitis.