We report a case of double primary malignancy, in which intracranial germinoma and thymoma occurred successively and independently. As curative therapies, the former lesion was treated by definitive irradiation and the latter by postoperative irradiation. Excellent local control has been maintained for 79 and 49 months, respectively, since the beginning of the radiotherapy. The accumulated dose to the thoracic spinal cord was 63.5 Gy. No symptoms suggesting the onset of radiation myelopathy, the most critical late radiation injury, have been observed up to now. We also investigated radiobiological effect to the spinal cord assessed by the formulae of CRE and TDF.