Endoscopic submucosal dissection (ESD) has become one of the standard treatments for early gastric cancer, and it has become increasingly important to accurately determine the depth of lesion infiltration prior to treatment, with endoscopic ultrasound (EUS) being the most recognized and reliable means of examination. ESD is technically feasible for patients with suspected submucosal infiltration after EUS, but an accurate and comprehensive pathological examination of the specimen is necessary. Mucosal resection is safe for differentiated intramucosal carcinoma without ulceration of any size or for differentiated intramucosal carcinoma with combined ulceration of less than 3 cm, whereas its risk of lymph node metastasis is present for submucosal carcinoma (SM1) without ulceration of less than 3 cm (especially 2-3 cm); in addition, mucosal resection is more controversial for undifferentiated intramucosal carcinoma (M) without ulceration of less than 2 cm.