Abstract: Objective To study the detection of lymph node micrometastasis in N0 colorectal cancer patients and its clinical significance in these patients. Methods In the study,453 lymph nodes obtained from 45cases of N0 colorectal cancer going curative operation were examined,using fluorescent quantity polymerase chain reaction(FQ-PCR) assay to detect cytokeratin 20(CK20) mRNA expression for identifying micrometastasis. Results Micrometastasis was detected in 46 lymph nodes(10.2%,46/453) of 20 cases(44.4%,20/45).The presence of micrometastasis was correlated with invasion depth of primary tumor, but was not related to sex, age, size and differentiation of primary tumor. The mean follow2up time in the positive groups (20 cases) with microme2 tastasis and the negative groups (25 cases) without micrometastasis were 19. 6 and 22. 4 months respectively, but there were 7 cases post2operative recurrence, metastases and 5 cases died in positive groups (20 cases) with micrometastasis, only 1 case died because of recurrence or metastases in negative groups (25 cases) without mi2 crometastasis (χ2 = 7. 305, P < 0. 05) . The disease2free survival of positive and negative groups was 75. 0 % (15/ 20) and 96. 0 %(24/ 25), respectively. The two groups have significant difference (χ2 = 4. 240, P < 0. 05) . Conclusion 　CK20 FQ2PCR assay is a sensitive and specific method to detect lymph node micrometasta2 sis in the patients with N0 colorectal cancer. The detection of CK20 mRNA in lymph nodes may contribute to improve the accuracy of clinical staging, determine patients' prognosis and provide information for rational adju2 vant therapy.