We describe a case of postradiation chondrosarcoma after basal cell carcinoma treatment. At the time he presented, the patient was a 35-year-old man who had received radiotherapy at a dose of 70 Gy for 8 weeks. Six months after radiation treatment, a rapidly growing mass at the upper right alveolar ridge of the gums, where radiation had been given, was diagnosed as chondrosarcoma. Generally, chondrosarcoma occurs after a latency period of several years following radiation. However, there are a few relevant reports indicating that maxillofacial chondrosarcoma can develop after radiotherapy for basal cell carcinoma, with a short latency of 6 months. We hypothesize that the dosage and treatment time of radiation may have played a role in the opening/closing of the Hh-signaling pathway in the case of this patient.