PURPOSE: Lymph-node metastasis is one of the most important prognostic factors in gastric cancer. However, it can be missed with conventional histologic examination with hematoxylin-eosin staining. Several methods have been introduced to improve the detection rate of micrometastasis. Among them, immunohistochemical staining with the anti-cytokeratin antibody is known to be an easy and useful method. METHODS: We used immunohistochemical staining with the anti-cytokeratin antibody to evaluate the incidence of micrometastasis in 48 patients with advanced gastric cancer who had been diagnosed as lymph-node negative by H&E, and its relationship to various clinicopathologic factors. RESULTS: Lymph-node micrometastasis (anti-cytokeratin antibody positive) was found in 15 (31.3%) of the 48 patients and in 33 (1.75%) of 1884 lymph nodes. Among the clinicopathologic variables, only lymphatic invasion was significantly associated with micrometastasis status. The gender, the age, the tumor size, the location of the tumor, the histologic type, and the depth of invasion were not significantly associated with micrometastasis status. During the average follow-up period of 21 months, 6 patients suffered a recurrence, and 2 of these patients died of the cancer recurrence. The recurrence and mortality rates were not significantly associated with micrometastasis status. CONCLUSION: Micrometastasis in stomach cancer was frequent when the primary tumor had invaded the lymphatic vessels.