 1. Introduction The aim of the study is to evaluate the efficacy and safety of ESD by use of a new water-jet assisted ESD system using the HybridKnife in patients with early gastric neoplastic lesions in comparison to the conventional ESD established in Japan. The water-assisted ESD technology allows pressure controlled injection of fluids through the tip of a recently developed HybridKnife. Submucosal injection, circumferential cutting and dissection of lesions as well as coagulation of bleeding can be performed with the same device without need for changing the instrument. These options should accelerate the procedure and may increase its safety and efficacy. 