An historical overview is given of the development of photodynamic therapy (PDT) with hematoporphyrin derivative for the treatment of malignant tumors. Results in patients with superficial, and non-superficial esophageal cancer and with early gastric cancer is described, with case illustrations and follow-up. Due to the difficulty in early stage diagnoses and in determining all cases of lymph node involvement, this form of treatment should be employed primarily in inoperable early-stage cancer, to reduce the extent of resection, or to render previously inoperable cases operable. Combination with other treatment modalities and the effects of PDT on histologically different tumor types, need to be further examined.