The method of tangential rotation therapy for non-operated breast cancer has been developed in Yonsei CancerCenter. This method is in principle to avoid the disorder of the lung field by radiotherapy as well as possibleand to make an adequate radiation dosage according to each treated region, including breast, axilla, supra orinfraclavicullar fossa, and sternum. We have various irradiation methods conducted today, but this continuous andrepeated tangential rotation therapy is extraordinarily superior to a traditional fixed tangential therapy. Theadvantages of this method are summarized as follows; 1) Simultaneous treatment with different doses is possible tothe breast and the thorax including the sternum. 2) The radiation effect on the intrathoracic organs includinglung and heart is almost absent. 3) It is easy to simultaneous irradiation in the large treated region. 4) Thedose distribution of various types is possible by changing a rotation angle and an eccentric angle in accordancewith irradiated region. 5) The irradiated fields are not overlapped and not so complicated as a fixedpolytagenital therapy. Therefor the continuous and repeated tangential rotation therapy is an adequate method forthe non-operated breast cancer and may be sure of helping for radiation therapy.