Abstract: Objective: To analyze the clinical and dosimetric predictive factors for radiation-induced esophageal injury in patients with non - small cell lung cancer (NSCLC) during three-dimensional conformal radiotherapy (3D-CRT).Methods: A total of 208 consecutive patients(146 menand 62 women) with NSCLC, treated with 3D-CRT, were analyzed retrospectively. The median age ofthe patients was 64 (range 35-87). The clinical and treatment parameters including gender, age,performance status, sequential chemotherapy, concurrent chemotherapy, presence of carinal orsubcarinal lymph nodes, pretreatment weight loss, mean dose to the entire esophagus, maximal pointdose to the esophagus, and percentage of volume of esophagus receiving>55Gy were studied. Clinicaland dosimetric factors for radiation-induced acute and late grade 3-5 esophageal injury were analysed,according to Radiation Therapy Oncology Group (RTOG) criteria.Results: Twenty- five (12%) of the208 patients developed acute or late grade 3-5 esophageal injury, among which, 9 patients had bothacute and late grade 3-5 esophageal injury and 2 died of late esophageal perforation. Concurrentchemotherapy and maximal point dose to the esophagus≥60Gy were significantly associated with theesophageal injury. Fifty-four (26%) of the 208 patients received concurrent chemotherapy, amongwhich 25 (46%) developed grade 3-5 esophageal injury (P<0.01). No grade 3-5 esophageal injury occurred in patients who received a maximal point dose to the esophagus <60Gy (P<0.01).Conclusion:Concurrent chemotherapy and the maximal esophageal point dose≥60Gy significantly related to the riskof grade 3-5 esophageal injury in patients with NSCLC treated with 3D- CRT.