Abstract: Objective 　This prospective study was performed to evaluate a simple sensitive and observer-independent polymerase-chain-reaction (PCR) based method for the detection of tumor cells in clinical specimens of regional lymph nodes. Methods 　Regional lymph nodes of 30 consecutive patients without neoadjuvant therapy were removed by systematic lymphadenectomy during resection of primary NSCLC. 100 of these lymph nodes were cut into two equal halves which were subsequently examined using either routine histopathology or real-time reverse transcriptase PCR ( real-time RT-PCR) . Real - time RT-PCR amplification of cytokeratin 19 (CK19) transcripts in a Light-Cycler inst rument was applied for the detection of tumor cell-specific RNA in lymph nodes. 18 lymph nodes of 12 patients with benign lung diseases served as negative controls. 15 primary tumor tissues of patient s with NSCLC served as positive controls. Results 　Histopathology showed that 94 (94. 0 %) lymph nodes were tumor-free. CK19 real time RT-PCR detected disseminated tumor cells in 26 ( 27. 7 %) of the histopathological tumor-free lymph nodes. Among the 6 lymph nodes which were histopathologically tumor - positive, all 6 (100 %) lymph nodes exhibited CK19 t ranscript s in the real-time RT-PCR. Histopathology showed that 22 (73. 3 %) patients had a pN0 status. CK19 real-time RT-PCR detected disseminated tumor cells in 13 (59. 1 %) of these pN0 patients. Conclusion 　CK19 real-time RT-PCR is a sensitive and specific tool for the detection of disseminated tumor cells in regional lymph nodes of patient s with operable NSCLC.