Endoscopic mucosal resection (EMR) has been accepted as a treatment of early gastric cancer (EGC). The number of EMR procedures for EGC has been increasing because a patient's quality of life after EMR is superior to that after surgical gastrectomy. In Japan, most EMR have been performed using the strip biopsy method; however, in some cases we experienced local recurrences when multiple fragments had been resected by this method. Single-fragment resection is preferable for correct histological diagnosis and a patient's prognosis. Recently, dramatic changes have occurred in the operational technique and design of the accessory apparatus. In 1996, we developed a special endoscopic knife, called the insulation-tipped electrosurgical knife (IT knife), which consists of a conventional diathermic needle knife with a ceramic ball at the top to minimize the risk of perforation. This knife can cut submucosa safely and remove a lesion completely. We named this method endoscopic submucosal dissection (ESD). Using this procedure, 96% of the tumors (471/488) were completely resected in one piece. During the follow-up period, there were no recurrent cases. One-piece resection by ESD using the IT knife improves the quality of life and prognosis for patients with early gastric cancer.