Technical innovation in radiation therapy (RT) such as stereotactic irradiation, intensity modulated RT, image-guided RT, and brachytherapy using remote controlled after-loading system have made it possible to deliver ideally distributed radiation dose to the target with great accuracy, while sparing the adjacent organs at risk. As a result, tumor control rate by RT improved markedly and became excellent alternative to surgery for asymptomatic or mildly symptomatic brain tumors, early stage lung cancer, and low-risk prostate cancer. In locally advanced stage of cancer, randomized controlled trials established the chemoradiation therapy as a standard treatment option for patients with head and neck cancer, lung cancer, esophageal cancer, and cervical cancer. RT is also a valuable treatment for palliation of local symptoms caused by cancer with consistently high response rates. Minimally invasive therapy has come to be emphasized its needs in the background of increased tendency of elderly patients with cancer, and advances in conformal dose delivery technique raise the RT at a more important position in cancer therapy. However, adequate number of RT profession is indispensable to utilize highly-sophisticated RT technology. Substantiality of an education system for radiation oncologist, RT technologist, and medical physicists is our current most important issue. J. Med. Invest. 57: 1-11, February, 2010