Endoscopic resection of tumoral lesions at an early stage is an accepted method. Among several methods of endoscopic resection, Endoscopic Submucosal Dissection (ESD) has been developed to remove the lesions in an ‘en bloc’ fashion regardless of size, shape, co-existing ulcer, and location. Several knives for endoscopic submucosal dissection are available and each of them has some merits and demerits. In this lecture, Dr. Yahagi presents his experience in ESD for GI tumors using dual knife.