© Mashhad University of Medical Sciences.Introduction: The current study aimed to compare the performance of radiobiological models in predicting acute esophagitis (AE) complications after three-dimensional conformal radiation therapy (3D-CRT). Material and Methods: Out of a total of 100 patients, 50 patients with concurrent chemotherapy and 50 patients without such therapy were treated with different total doses and a daily dose range of 1.8-2.4 Gy on the basis of 5 days a week for 3 months. Predictions of AE were based on Lyman-Kutcher-Burman (LKB) and equivalent uniform dose (EUD)-based radiobiological models. Consequently, 3 months of follow-up were performed to monitor the complication incidence among the studied patients. Receiver operating characteristic (ROC) and univariable logistic regression analyses were carried out to determine the effect of mean dose, volume percentage, and weight loss percentage on the probability of AE grade ≥ 2. Results: The EUD-based model showed a better concordance with the clinical data for all patients (area under the curve [AUC]=0.919) and the concurrent chemoradiotherapy (CCRT) group (AUC=0.986). For the radiation therapy group, the LKB model had a better performance than the EUD-based model (AUC=0.921). Grade ≥ 2 esophagitis occurred 37.94±4.0 and 68.39±7.1 days after the initiation of radiation therapy in the chemoradiation and radiation therapy groups, respectively. Conclusion: The EUD-based model showed a higher agreement with the follow-up data. The incidence time of grade ≥ 2 AE in the CCRT was approximately two times shorter than that in the non-CCRT group.