To study the influence of the number of metastatic lymph nodes (LNs) on survival and International Union Against Cancer tumor-node-metastasis (TNM) classification for esophageal carcinoma. The clinicopathological data on 1146 patients with esophageal squamous cell carcinoma who had undergone an esophagectomy were retrospectively studied. Survival was analyzed by the Kaplan-Meier method. By subclassifying the nodes (N) category according to the number of metastatic LNs as: N0 for no LN metastases; N1(1) for only one positive node; and N1(2) for >or=2 positive nodes. TNM staging was refined as stage IIa (T2-3N0M0), stage IIb (T1N1M0 and T2N1(1)M0), stage IIIa (T2N1(2)M0 and T3N1(1)M0), and stage IIIb (T3N1(2)M0 and T4NanyM0), and the survival was analyzed. LN metastases was found in 380 of 1146 (33.2%) treated esophageal cancer patients. In 4270 LNs harvested, metastases was detected in 807 (18.9%). The 5-year survival rates of the patients with 0, 1, and >or=2 positive nodes were 59.8, 33.4, and 9.4%, respectively. There was statistically significant difference among these three groups. The 5-year survival of the patients in stages T2N1M0 and T3N1M0 was significantly higher in the N1(1) group than in the N1(2) group (41.5 vs 24.1%, and 31.2 vs 6.8%, P<0.001). The 5-year survival rates of the patients in refined stage IIa, IIb, IIIa, and IIIb were 57.1, 42.2, 28.6, and 8.5%, with significant difference existing in each stage groups. The number of positive LNs significantly influenced survival of the patients with esophageal cancer. Three grade classification (0, 1, >or=2 positive nodes) could quite well demonstrate the effect of the number of LN metastases and the survival. The refined TNM classification based on the number of LN metastases could better reflect the prognosis of esophageal cancer. Our results offer a strong rationale for refining the International Union Against Cancer TNM classification for esophageal carcinoma.