Objective:To investigate the clinical value and significance of immunohistochemical(IHC) techniques and reverse transcriptase-polymerase chain reaction (RT-PCR) testing for detecting micrometastases of regional lymph nodes in patients with gastric cancer. Methods:A total of 1 835 lymph nodes taken from 85 patients with average of 21.7 nodes per case were detected by IHC and RT-PCR assay to detect cytokeratin 20 markers. Clinicopathologic parameters and prognosis were compared between patients with and without micrometastases. Results:The incidence of nodal micrometastases increased from 75.3% by hematoxylin-eosin (HE) staining to 83.5% and 90.6% respectively by immunostaining and RT-PCR in 85 patients with gastric cancer.The presence of micrometastases was closely correlated with Lauren classification and tumor depth, but was not correlated with tumor site and size. The re-stage rate was 18.8% and 37.6% respectively by immunostaining and RT-PCR. Eighty-two patients were followed up at an average time of 21.2 months. Lymph nodal micrometastases seemed to be a little prognostic value in patients with gastric cancer. Conclusions:The present Results: indicate that immunohistochemical staining and RT-PCR assay are useful tools for the detection of micrometastases in the patients with gastric cancer,and may be used to improve the staging system for gastric cancer, and also serve as the basis for decision of therapautic regimen.