This book, now in a revised and updated second edition, provides a comprehensive summary of recent progress in boron neutron capture therapy (BNCT). BNCT is based on the ability of the non-radioactive isotope boron-10 to capture thermal neutrons with very high probability and to release instantaneously two heavy particles with a path length of one cell diameter or less. This in principle allows for tumor cell-selective high-LET particle radiotherapy. In the past BNCT depended solely on fission reactor-based irradiation facilities, but the appearance of accelerator-based neutron sources placed in hospitals has opened a new chapter for BNCT. This edition covers all the important aspects of BNCT, including neutron sources, boron chemistry, drugs for BNCT, boron analysis and imaging, dosimetry, and radiation biology. The use of BNCT in a variety of malignancies and also some non-malignant diseases is extensively discussed. BNCT is clearly shown to be a promising modality at the threshold of wider clinical application. All of the chapters are written by experienced specialists in a language that will be readily understood by all participating disciplines.