The success of boron neutron capture therapy (BNCT) depends mainly on sufficient spatial biodistribution of boron (B-10) localized around or within neoplastic cells to produce a high dose gradient between the tumor and healthy tissue. Contrary to what is usual in radiotherapy, BNCT proposes treatment planning directed at the cell rather than the tumor mass. However, it is not yet possible to precisely determine the concentration of B-10 in a specific tissue in real-time using non-invasive methods. Some critical issues still need to be resolved if BNCT is to become a valuable, minimally invasive, and efficient cancer treatment. This review article provides an overview of the funda-mental principles, recent advances, and future directions of BNCT as a cell-targeted cancer therapy. The main emphasis is on topics related to biological dosimetry, methods for assessing boron concentration, mechanisms of action of BNCT, and its physical bases for clinical implementation.