BACKGROUND & OBJECTIVE Radiotherapy is an effective treatment for lung cancer. It is still uncertain whether gemcitabine can improve the efficacy of radiotherapy on lung cancer. This study was to investigate the efficacy of gemcitabine with concurrent radiotherapy on stage III, inoperable non-small cell lung cancer (NSCLC), and observe the adverse events and long-term survival of the patients. METHODS Sixty patients were enrolled and divided into trial group (30 cases) and control group (30 cases). In trial group, the patients received weekly administration of gemcitabine (400 mg/m(2)) with concurrent radiotherapy at a total dose of 60-66 Gy (2.0 Gy dose fraction per day, 5 days per week). In control group, the patients received only radiotherapy at the same dosage. The responses were evaluated according to WHO criteria. The efficacy, adverse events and long-term survival between the 2 groups were compared with Chi(2) test. The long-term survival was also estimated by Kaplan-Meier method. RESULTS Fifty-eight patients finished the trial. The follow-up rate was 96.7%. The response rate was 70.0% in trial group and 60.0% in control group (P>0.05). There was no significant difference in the incidence of hematologic and non-hematologic adverse events between the 2 groups (P>0.05). The 1-, 2-, and 3-year survival rates were 77.7%, 58.6%, 26.4% in trial group, and 70.3%, 30.1%, 16.1% in control group (P>0.05). CONCLUSIONS In this study, gemcitabine with concurrent radiotherapy, as compared with radiotherapy alone, prolonged the survival of stage III, inoperable non-small cell lung cancer patients, but the improvement is not significant. In both groups, the adverse events are tolerable.