The aim of this study was to retrospectively analyze and assess the outcomes and prognostic factors of radiotherapy in patients with node-positive thoracic esophageal squamous cell carcinoma after radical surgery. One hundred twenty-six patients with node-positive thoracic esophageal squamous cell carcinoma who had undergone adjuvant therapy (postoperative radiotherapy alone or postoperative sequential chemoradiotherapy without receiving postoperative concurrent chemoradiotherapy) after radical surgery, were retrospectively reviewed from January 1996 to December 2003. Univariate and multivariate analyses were performed using log-rank and Cox proportional hazard models, and survival curves were estimated using the Kaplan-Meier method. The 1-, 3- and 5-year overall survival rates of all 126 patients were 71.4, 39.1, and 22.0%, and disease-free survival rates were 64.3, 36.4, and 21.5%, respectively. Lymph node ratio (the ratio of the number of metastatic lymph nodes to the number of lymph nodes removed, LNR) > or = 0.2 (P= 0.006), pT3 + pT4 (P= 0.06) and sequential chemoradiotherapy (P= 0.08) were associated with a poorer survival by univariate analysis. In multivariate analysis, LNR (P= 0.01, hazard ratio = 0.57, 95% confidence interval, 0.37-0.87) and tumor depth of invasion (P= 0.03, hazard ratio = 0.62, 95% confidence interval, 0.41-0.96) were the independent predictors of survival. Sequential chemoradiotherapy receded survival tendency without significant difference (P= 0.09, hazard ratio = 0.64, 95% confidence interval, 0.37-1.08). Therefore, LNR and tumor depth of invasion were the independent prognostic factors of radiotherapy in patients with node-positive thoracic esophageal squamous cell carcinoma after radical surgery. The addition of chemotherapy does not seem to confer a survival benefit.