[Contribution to the discussion about the induction of tumors by ionizing radiation (author's transl)].

The authors describe six observations of malignant tumors which had appeared in the region of the irradiation fields after a period of 11 to 51 years following to a radiotherapy. The doses were between approximately 2000 and 9000 R resp. rd. The individual tumors were: one osteogenic sarcoma, one chondrosarcoma, two fibrosarcomas, one lymphangio-hemangio-sarcoma and one basal cell carcinoma. According to the present state of our knowledge about the induction of tumors by ionizing radiation, we presume that no threshold dose does exist and that the danger of a tumor induction increases with the dose. The function of the tumor induction is still in general discussion.