Abstract: Telomeres are protective caps located at the ends of human chromosomes. Telomeres shorten with each successive cell di -vision in normal human cells, whereas they are continuously elongated by human telomerase in over 85% of tumors. This simple and attractive difference steers the development of anticancer drugs targeting telomeres and telomerase. Many promising current telo -mere/telomerase- targeting agents, such as GRN163 L and GV 1001, showed good therapeutic effect both in preclinical studies and phase Ⅰ/Ⅱclinical trials. These agents have even entered phase Ⅲclinical trials in patients with various tumors. Most therapeutics are more effective when used in combination with standard chemotherapies. Moreover, pharmacological interference with tumor-cell telomere biology to reduce telomere length and/or telomere stability could enhance the effectiveness and safety of radiotherapy. Therapeutics targeting telomere/telomerase may play a key role in radiotherapy in the era of personalized medicine in the future.