Background: The 7th edition American Joint Committee on Cancer tumor-node-metastasis (AJCC TNM) staging system was published in 2010. Here we evaluate its predictive ability and compare the 6th and 7th editions of the AJCC TNM staging systems in esophageal squamous cell cancer (ESCC) with preoperative radiotherapy. Methods: A total of 296 esophageal squamous cell carcinoma patients receiving preoperative radiotherapy between 1980 and 2007 were included. Patients were staged using the 6th and 7th edition staging systems. Survival analyses were performed using Cox regression models. The homogeneity, discriminatory ability, and monotonicity of gradients of the two staging systems were compared using linear trend χ2, likelihood ratio statistics, and Akaike information criterion calculation. Results: The overall five-year survival rate for the entire cohort was 27.1%. Female gender, length, "T," and "N," classifications according to the 7th edition staging system were the prognostic factors in univariate analyses. However, tumor histological grade and cancer location did not significantly influence patient survival. The 7th edition staging system has the highest linear trend χ2 and likelihood ratio χ2 scores. Compared to the 6th edition, the 7th edition staging system also has a smaller Akaike information criterion value, which represents the optimum prognostic stratification. Conclusions: The strength of the 7th edition AJCC TNM staging system lies in the new descriptors for "T" and "N" classifications. However, we did not find cancer location to be a significant prognostic factor in our cohort. Overall, the 7th edition AJCC TNM staging system performed better than the previous edition. © 2013 Tianjin Lung Cancer Institute and Wiley Publishing Asia Pty Ltd.