Abstract: Objective: To evaluate the effect of radiotherapy on non-small-cell lung cancer(NSCLC) in the elderly.Methods: From Nov.1998 to Dec.2000,83 patients over sixty were randomized into conventional radiotherapy plus three-dimmentional conformal radiotherapy(3DCRT) group and conventional radiotherapy(CT) group.The two groups were initially treated by the same conventional radiotherapy at a dose of 40 Gy,20 fractions for four weeks.The patients in 3DCRT group were then administered 3DCRT in 3.0 Gy/f,5 fractions a week at a dose of 24 Gy.The patients in CT group received the same CT at a dose of 20 Gy,10 fractions for two weeks.Results: The 3-year survival rates were 36.6% in the 3DCRT group and 14.3% in the CT group.The difference of the two groups was significant(P<0.05).There was no grade Ⅲ or Ⅳ radiation esophagitis in the 3DCRT group.The incidences of acute radiation pneumonitis and radiation pulmonary fibrosis was 7.3% and 39% respectively in the 3DCRT group.Conclusions: In treatment of NSCLC in the elderly,conventional radiotherapy followed by 3DCRT may increase the 3-year survival rate and decrease the acute and late radiation reaction.