Objective: To retrospectively evaluate the clinical and dose-volumetric parameters for association with risk of the acute radiation pneumonitis and late radiation lung injury in patients after three-dimensional conformal radiotherapy(3D—CRT) for Squamous Cell Carcinoma(SCC)of the thoracic middle and lower esophagus. Methods: Data from 56 patients(41 men, 16 women;median age, 64 years; range，31-81 years)newly diagnosed with SCC of the esophagus and treated with 3D-CRT between January 2002 and June 2004 in our hospital were retrospectively analyzed. Radiation lung injury was scored by using Radiation Therapy Oncology Group criteria. Clinical parameters were analyzed. Dose-volumetric parameters analyzed were percentage of lung volume that received a dose from 5Gy or more(V5)to 50Gy or more(V50); mean lung dose (MLD); and total dose et al．X2 test was performed to compare clinical parameters between patients who developed severe radiation lung injury and those who did not. Univariate and multivariate logistic regression analyses were performed to evaluate data for association between dose-volumetric parameters and acute severe radiation lung injury. Spearman X <2> test was used to assess data for correlations among dose-volumetric parameters. P≤0.05 was considered to indicate statistically significant difference. Results: Of 56 patients, 7(12.5％)developed acute radiation pneumonitis of grade 2;3(5.4％), grade 3. None had grade 4.14(25.0％)developed late radiation lung injury. 1. Univariate analysis showed that X-ray esophageal lesion length, the prescribed dose, V5- V25, MLD, Esophageal PTVD90, PTVV50 and the total number of field beams were significantly differ between patients who developed severe acute radiation pneumonitis and those who did not. X-ray length of esophogeal lesions, lung V5-V40, MLD and combined with chemotherpapy were sgnificantly differ between patients who developed severe late radiation lung injury and those who did not. 2. In multivariate analysis: V25, the total number of field beams and X- ray lesion length were the variable associated with severe acute radiation pneumonitis. V30 and combined chemotherapy were the variable associated with late radiation-induced lung injury. 3. Acute radiation peumonitis and late radiation lung injury have no obvious correlation. 4. Acute radiation pneumonitis and late radiation lung injury no obvious impact on the over survival rate. Conclusions: V25, the total number of field beams and X-ray lesion length are useful indicators of risk for development of late radiation lung injury after 3D conformal radiotherapy in patients with esophageal cancer.