Recurrences of adenocarcinoma of the esophagogastric junction are frequent even in patients who are classified as pN0 after radical resection, suggesting that occult nodal metastases may have been missed on routine histologic examination. Immunohistochemical analysis using antibodies to cytokeratin was retrospectively performed in 1301 lymph nodes from 46 patients who underwent surgical resection for adenocarcinoma of the esophagogastric junction through a laparotomy and a right thoracotomy. Compared to routinely stained sections, the total number of metastatic lymph nodes was significantly (P = 0.0001) increased when both serial sectioning and anticytokeratin immunohistochemical analysis were performed. Overall 6 (33.3%) of the 18 patients previously considered N0 were recategorized as N1 for the presence of micrometastases to lesser curvature nodes. Three of these patients had recurrent disease within the first year of follow-up. Both the probability of survival or no recurrence and the disease-free survival were significantly greater in patients in whom the ratio of invaded to removed lymph nodes was less than 0.2. Anticytokeratin analysis identified occult nodal metastases in one third of our patients with adenocarcinoma of the esophagogastric junction. This modified tumor staging and had an impact on overall and disease-free survival.