The definition of cancer at the esophagogastric junction has been discussed for over 30 years. Although at present, two classifications advocated by Nishi or Siewert have been used, these classifications are still controversial from the viewpoints of anatomy, physiology, histology, diagnosis and treatment. We should analyze a large number of patients based on the same definition of cancer at the esophagogastric junction. Adjustment of the Japanese rules for cancer of the esophagus and stomach is necessary, and a treatment strategy should be established for cancer at the esophagogastric junction.