AbstractDefinition, macroscopic and histologic classification, diagnosis, surgical treatment, and prognosis of early gastric cancer are described. The definition and macroscopic classification were agreed upon by endoscopists, pathologists, radiologists, and surgeons at the meeting of the Japanese Gastroenterological Endoscopy Society in 1962. Early gastric cancer was grossly classified into 3 major types, based solely on surface characteristics in order to make the classification usable for radiologists and endoscopists. Since most early gastric cancers are asymptomatic, mass survey examinations are of value. Patients with a suspicious lesion or symptoms should undergo a thorough diagnostic workup that includes x‐ray studies, endoscopy, and biopsy for histologic examination. The aim of surgery is complete eradication of cancer cells. Since peritoneal dissemination and liver metastases are rare, surgery is directed at removing regional lymph nodes with possible metastases and not leaving any cancer cells at the gastric suture line. Although the incidence of metastases to regional lymph nodes is reported to be about 5% and of lymphatic permeation to be about 12%, 5‐year survival rates ranging from 89 to 95% have been achieved.