**Abstract**

Boron neutron capture therapy (BNCT), which uses the capture reaction between neutrons and boron-10, an isotope of boron, is rapidly gaining interest. The reason for this is the successful development of a compact accelerator-type neutron generator that can be installed in a hospital and launched into the clinical setting. BNCT, which provides selective radiotherapeutic effects at the cellular level, is expected to be effective against invasive cancer. We have been investigating BNCT applications in various types of malignant brain tumors, especially malignant gliomas, as medical applications. Recently, we have conducted clinical trials using the developed accelerator neutron source. Research on pharmaceutical applications of compounds that transport boron to cancer cells is expected to be in even greater need. Currently, the only boron agent used in cancer therapy is BPA (Borofaran 10B), which takes advantage of the demand for essential amino acids, but the research and development of boron agents are an absolutely key technology to further improve the precision of this treatment modality. This chapter summarizes and discusses the results of BNCT in the treatment of brain tumors.

**Keywords:** boron neutron capture therapy, Borofaran (10B), brain tumor, glioma, accelerator-type neutron generator, nuclear reactor
