Abstract: Objective: To evaluate whether primary tumor radiation during a course of chemotherapy would result in longer survival for stage Ⅳ non-small-cell lung cancer(NSCLC) patients. Methods: From December 1999 to January 2004, data from a total of 188 stage Ⅳ NSCLC patients were collected. All of the patients received 3-10 cycles of platin-based chemotherapy. They were divided into 2 groups: the RT group (63 cases) that received primary tumor radiation during a course of chemotherapy, and the non-RT group (125 cases) that received chemotherapy alone. Overall survival rate and safety were evaluated. Results: The mean 1-year survival rate(SR) of all patients was 48.9%, and the median survival(MS) was 12 months(8-23 months). SR was 77.8% in the RT group, and 41.6% in the non-RT group. MS was 15 months in the RT group, and 10 months in the non-RT group. There was a significant difference in SR between the two groups(P=0.025). There were 74 patients(37 cases in each group) who had partial responses (PR) after chemotherapy, with a MS of 17 months in the RT group and 13 months in the non-RT group. The 1-year survival rate was 84.2% in the RT group and 66.7% in the non-RT group(P=0.454). In the patients who had stable disease(SD) after chemotherapy, the MS was 12 months for the RT group and 8 months for the non-RT group, and the 1-year survival rate was 45.0% and 24.6%, respectively. The difference was statistically significant (P=0.0027). Conclusion: Our data showed that primary tumor radiation administered during a course of chemotherapy can improve the overall survival of stage Ⅳ NSCLC patients, especially those with stable disease after chemotherapy alone.