From 1976 to 1985, 185 patients with non-small cell lung cancer at stages I-III were treated with definitive radiotherapy in Gunma University Hospital. As a result of analyzing the long-term survivors treated with radiotherapy, suitable conditions of the patients for radical radiotherapy were as follows; 1) stage I or II, and some stage III, 2) as regards the histologic type epidermoid carcinoma or well-differentiated adenocarcinoma, 3) as regards the primary sites, the upper lobe and the superior segment of the lower lobe, 4) the optimum dose was 60-70Gy, 5) the size of the radiation fields given > 40Gy was 100 cm2 or less, and 6) the host condition was satisfactory (BRM combined use). In particular, as a result of administering PSK as adjuvant treatment to patients with epidermoid carcinoma of the lung showing satisfactory tumour shrinkage after radiotherapy, the five year survival rate of the patients with stages I or II disease, as well as stage III was 39% and 22% respectively, compared with the non-administered group's 16% and 5%. These differences are statistically significant. Although an improvement in the results of treatment with the combined use of appropriate BRMs is anticipated in the future, when clinical trials for combined BRM and radiotherapy are planned, the subjects should be patients with satisfactory tumour regression after radiotherapy.