Boron neutron capture therapy (BNCT) is a neutron-based technique that allows selective cancer treatment at the tumour cellular level. BNCT is especially suitable for the treatment of brain, head, neck and skin cancers. Using the reaction between a neutron and boron to selectively destroy cancer cells, BNCT is a treatment that differs radically from conventional radiotherapy and promises to become a more widely adopted option for cancer treatment. BNCT is undergoing a major resurgence of interest around the world as some recent progress in accelerator technology allows the procedure to be undertake in clinics. In addition, the approval of BNCT in Japan as a routine clinical treatment for certain tumour types offers valuable insights for other states considering a similar approach. This publication comprehensively reports on the current state of the science as well as the supporting technology. It covers accelerator-based neutron sources, beam design, physical dosimetry, facility design and operation, pharmaceuticals, radiobiology, dose calculation, treatment planning and clinical trials. It has been written to assist in decision making at the national level as well as offering practical guidance for all those involved in implementation and ongoing management of BNCT programmes.