Accurate prognostication is important to determine the curability and appropriate extent of surgery in gallbladder cancer because effective systemic therapy has not been established and surgical resection is the only effective treatment for this disease entity. It is well known that the survival outcomes after curative resection of gallbladder cancer are strongly associated with the depth of tumor invasion through the gallbladder wall. In particular, tumor biology plays a far greater role in outcome than does the extent of resection in T2 gallbladder cancer. Thus, the extent of resection and necessity of adjuvant therapy should be determined according to the likelihood of microscopic liver metastases or nodal involvement in individual patients. Major changes in the latest version of the American Joint Committee on Cancer (AJCC) staging system for gallbladder cancer included subdivision of T2 disease according to the anatomic location of tumor and re-definition of N factor according to the number of positive lymph nodes. Because the gallbladder has a unique anatomical position, with half of its body being attached to the liver, the risk of tumor invasion and the mode of cancer spread are influenced by whether the tumor is located on the hepatic side or the peritoneal side of the gallbladder. In addition, recent studies have clarified that the number of lymph node assessment, rather than the location of the lymph nodes, may better dictate the nodal category. In this talk, reported evidence supporting the current version of AJCC staging system and future perspective will be discussed.