Photodynamic therapy is a fascinating concept that will continue to occupy many research groups around the world in coming years. Although a widespread clinical application for the method has not yet emerged, there are good prospects that photodynamic therapy will establish itself at major gastroenterologic centers as an endoscopic procedure with few or no side effects in the treatment of Barrett's esophagus (sever dysplasia and early carcinoma) and, in selected cases, for the treatment of early gastric carcinoma.