[en] The Heavy Ion Medical Accelerator in Chiba (HIMAC) is the world's first heavy ion accelerator complex dedicated to medical use in a hospital environment. Heavy ions have superior depth-dose distribution and greater cell-killing capability than other forms of radiation. In June 1996, clinical research for the treatment of bone and soft tissue sarcomas was begun using carbon ions generated by the HIMAC. As of February 2010, a total of 507 patients with bone and soft tissue sarcoma were enrolled in these clinical trials. Most of the patients had locally advanced and/or medically inoperable sarcomas. The clinical trials revealed that carbon ion radiotherapy provided definite local control and offered a survival advantage without unacceptable morbidity for patients with bone and soft tissue sarcomas that were hard to cure using other modalities. (author)