To study micrometastases in lymph nodes from patients with node-negative gastric carcinoma by routine histologic examination and discuss their prognostic significance and the relationship between micrometastases and each of the clinicopathologic factors. Methods: A total of 1245 perigastric lymph nodes from 105 patients with node-negative gastric carcinoma was immunohistochemically detected using a monoclonal antibody against low molecular weight cytokeratin AE1. The characteristics of the micrometastases, their related factors and effect on patients’ survival after surgery were analysed and tested with statistical methods. Results: Micrometastases were observed in 81 lymph nodes (6.5%) of 31 patients (29.5%). The incidence of lymph node micrometastases was significantly higher in the diffuse type (41.5%) than in the intestinal type gastric carcinoma (17.6%, P<0.01, x2 test). In addition, the presence of micrometastases was closely correlated with the size and invasion depth of the primary tumor, but had no relation to patient’s age, sex and the location of primary tumor. The patients with micrometastases had significantly worse prognosis shown by Log-rank test. Their five-year survival rate after surgery was 61.29%; for those without micrometastases the rate was 82.43%, P=0.0116. When the number of patient’s lymph nodes with micrometastases was three or more, the five-year survival rate of these patients was much lower (41.67%, P=0.0012). Conclusion: The detection of lymph node micrometastases is necessary to more accurately determine the prognosis and clinical staging of patients with node- negative gastric carcinoma by routine histologic examination. The presence of micrometastases may be regarded as one of the clues in adjuvant therapy of those patients.