BACKGROUND To analyze the clinical and dosimetric risk factors of acute esophagitis (AE) in non-small-cell lung cancer (NSCLC) patients treated with concomitant chemoradiotherapy. METHODS Seventy-six NSCLC patients treated with concomitant chemoradiotherapy were retrospectively analyzed. Forty-one patients received concomitant chemoradiotherapy with vinorelbine/cisplatin (VC), 35 with docetaxel/cisplatin (DC). AE was graded according to criteria of the Radiation Therapy Oncology Group (RTOG). The following clinical and dosimetric parameters were analyzed: gender, age, clinical stage, Karnofsky performance status (KPS), pretreatment weight loss, concomitant chemotherapy agents (CCA) (VC vs. DC), percentage of esophagus volume treated to ≥ 20 (V20), ≥ 30 (V30), ≥ 40 (V40), ≥ 50 (V50) and ≥ 60 Gy (V60), and the maximum (Dmax) and mean doses (Dmean) delivered to esophagus. Univariate and multivariate logistic regression analysis were used to test the association between the different factors and AE. RESULTS Seventy patients developed AE (Grade 1, 19 patients; Grade 2, 36 patients; and Grade 3, 15 patients). By multivariate logistic regression analysis, V40 was the only statistically significant factor associated with Grade ≥ 2 AE (p<0.001, OR = 1.159). A V40 of <23% had a 33.3% (10/30) risk of Grade ≥ 2 AE, which increased to 89.1% (41/46) with a V40 of ≥ 23% (p<0.001). CCA (p =0.01; OR = 9.686) and V50 (p<0.001; OR = 1.122) were most significantly correlated with grade 3 AE. A V50 of <26.5% had a 6.7% (3/45) risk of Grade 3 AE, which increased to 38.7% (12/31) with a V50 of ≥ 26.5% (p = 0.001). On the linear regression analysis, V50 and CCA were significant independent factors affecting AE duration. Patients who received concomitant chemotherapy with VC had a decreased risk of grade 3 AE and shorter duration compared with DC. CONCLUSIONS Concomitant chemotherapy agents have potential influence on AE. Concomitant chemotherapy with VC led to lower risk of AE compared with that using DC. V40 and V50 of esophagus can predict grade ≥ 2 and ≥ 3 AE, respectively.