Abstract: Boron neutron capture therapy (BNCT) is based on the nuclear reaction that ~(10)B is irradiated with neutrons of the appropriate energy to produce high-energy alpha particles and recoiling ~7Li nuclei. BNCT has been used clinically to treat patients with glioma and melanoma. It is reviewed that the principles of BNCT, tumor-targeted boron delivery agents, neutron sources, results of clinical trails, and it is discussed that the challenges and problems that must be faced if BNCT is to become a useful treatment modality for tumors.