[en] To decide the most suitable dose schedule of high dose rate interstitial radiotherapy (HDRISR) for the tongue cancer, we paid attention to the acute mucosal reaction after radiation therapy. There is the European Organization for Research on Treatment of Cancer/Radiotherapy Oncology Group (EORTC/RTOG) scoring system for the intraoral mucosal reaction after radiation therapy, but this scoring system does not assess the degree of the mucosal reaction adequately at the disapprearing phase. So we modify the scoring system at the disappearing phase of mucosal reaction. When the mucositis turns to disappear phase, the score is 3.5 and when the coating area reduces less than 50% area at the peak mucosal reaction, the score is 2.5. When the coating becomes transparent, the score is further reduced by 1 degree. When there is only erythema, the score is 1, and when reaction disappears completely, the score is 0. We observed 10 cases of tongue cancer treated with interstitital brachytherapy; 5 cases were treated with HDRISR and 5 cases were low dose rate interstitital radiotherapy (LDRISR). During the appearing phase, we used the EORTC/RTOG scoring system and during the disappearing phase, the new scoring system. This system reflected the mucosal healing course very well. (author)