Objective To investigate the detection of lymph node micrometastasis in stage Ⅰ nonsmall cell lung cancers (NSCLC) using lung-specific X protein (LUNX) mRNA as a marker based on reverse transcription-polymerase chain reaction (RT-PCR) and its relationship with the patho-clinical features and prognosis.Methods 52 patients underwent curative lobectomy,excluding pneumonectomy and Palliative resection.Curative lobeetomy included systemic lymph node reseetion,Which meant at least 6 mediastinal lymph node from 3 stations were reseeted.The expression of LUNX mRNA in each station of lymph node were examined by means of RT-PCR.LUNX mRNA was then used as a marker of lymph node micrometastasis.Analyses of relationship between lymph node micrometastasis and the pathoclinical features,overall survival and disease free survival were then carried out.Results The expression of LUNX mRNA:none was positive for all ten lymph nodes from benign diseases.All 52 lung cancer tissues showed positive expression,14.98％ of lymph nodes and 12.24％ of mediastinal lymph nodes showed positive expression,so that the LUNX stage was upgraded.Survival affecting factors included:LUNX stage (P ＜ 0.01),mediastinal lymph nodes micrometastasis (P ＜ 0.01),number of lymph nodes and mediastinal lymph nodes resected (P ＜ 0.05),pathological differentiation (P ＜ 0.05).Those with mediastinal lymph nodes micrometastasis had a 21.8 folds higher risk of death than those without (P ＜ 0.01).Conclusion The expression of LUNX mRNA in lymph nodes is related to overall survival and disease free survival,and is a reflection of lymph nodes micrometastasis.The subgroup of stage propidium iodide (PI) patients with high risks can be thus found.This technique is helpful in restaging patients more accurately.Survival can be improved if interference is applied in early stage.