Dr. Yahagi is a professor of medicine and a director, division of research and development for minimally invasive treatment at cancer center, Keio university school of medicine in Tokyo. Dr. Yahagi graduated from Niigata University School of Medicine and received M.D. in 1987. He completed residency program in general internal medicine at Tokyo Teishin Hospital in 1989 and stay one more year as a staff physician at the department of Gastroenterology in the same hospital. He moved to the University of Tokyo in 1990 as a faculty member of the 1st department of internal medicine and worked there for 15 years. During this period he accumulated his experience for endoscopy procedures and conducted basic research especially for gene cloning of enteropepitedase. He received his Ph.D. from the University of Tokyo in 1998 based on this basic research. In addition to basic research, he pioneered one of the original technique of ESD using a tip of thin type snare at the University of Tokyo. He was promoted as a director of gastroenterology department and endoscopy unit at Toranomon hospital in 2005 and he build up a very strong team for therapeutic endoscopy and conducted many ESD procedures. He moved to the Keio University as a professor of medicine in 2010 in order to carry on further investigation for minimally invasive treatment of GI tumors. Dr. Yahagi is not only one of the pioneer of ESD technique but also an inventor of many devices for ESD including flex knife, dual knife, dual knife J, endolifter and bipolar hemostatic forceps. He also developed new techniques of therapeutic endoscopy such as the water pressure method and the string clip suturing method. He has participated as an invited guest faculty member at many international meetings around the world.