Metastatic spread to cervical lymph nodes(LNs) is a major determinant of outcome in oral squamous cell carcinoma (SCC). To provide an useful method for the detection of lymph node micrometastases, we fulfilled the histopathological examination and reverse transcriptase polymerase chain reaction(RT-PCR) using the paraffin-embedded LNs of oral SCC patients. In this study, 78 LNs from 12 patients with primary oral SCC were analyzed. Metastases in the regional LNs were evaluated by RT-PCR for squamous cell carcinoma antigen(SCCA) and cytokeratin 5(CK5). Detectability of metastatic LNs by RT-PCR was compared with histopathological examination. Of 78 LNs, CK5 and SCCA mRNA were detected in 32(41.0%) and 8(10.3%), respectively. Histopathologically, 10(12.8%) of 78 LNs were positive. CK5 mRNA was detected in all 10 histopathologically positive LNs. In contrast, SCCA mRNA was detected in 5 of 10 histopathologically positive LNs. These findings suggest that genetic diagnosis by RT-PCR based on CK5 mRNA expression may be sensitive and clinically useful technique to detect the presence of metastatic carcinoma cells in regional lymph nodes of oral SCC.