Standard therapy for unresectable localized non-small cell lung cancer has been radiotherapy alone, but the treatment results were not satisfactory in terms of high incidence of distant metastasis and poor local control. Various kinds of prospective randomized clinical trials (RCT) were undertaken to solve the problems of encompassing the treatment field, total treatment dose, alteration of fractionation and combination of the chemotherapy drugs since 1970's. Radiation field which includes the primary site, ipsilateral hilar and mediastinal lymph nodes, and the total radiation dose of 60Gy in 6 to 7 weeks has been assumed as standard. However, with the advent of 3-dimensional treatment planning including the inverse planning method, particle radiotherapy and intraluminal brachytherapy, some trials are on-going to increase the total dose up to 70Gy or more in relation to the more confinement of the treatment field to the primary site only. Fractionation has also been studied to reduce the late normal tissue damage or to increase the total tumor dose, and is at present in favor of the accelerated hyperfractionation. Meta-analysis of the results of 11 RCT's revealed that the results with combination chemoradiotherapy including cisplatin yields longer MST, and higher 2-year survival rate.