Objectives:To investigate the possible mechanism of oral carcinogenesis and to explore the value of clinical application of the detection of CK19 for OSCC patients. Methods: The cancerous tissues, para-cancerous tissues and excisional lymph nodes were collected from 20 patients with OSCC. The total cell RNA was extracted and used to detect the expression of CK19mRNA by real-time FQ-PCR. Results: 1. CK19mRNA level in the group of cancerous tissues was 1.85 times higher than the group of normal oral mocosa. The same level between the para-cancerous tissues group and normal oral mucosa group was not significant.2. CK19mRNA level in the group of cancerous tissues were 1.66 times higher than the group of para-cancerous tissues.3. The expression of CK19mRNA level in the cancerous tissues relative to para-cancerous tissues of the patients whose CK19mRNA expression was 1.24 times lower than the patients whose CK19mRNA expression was negative in lymph nodes. The expression of CK19mRNA level in the cancerous tissues relative to normal oral mucosa of the patients whose CK19mRNA expression was 1.41 times lower than the patients whose CK19mRNA expression was negative in lymph nodes. The expression of CK19mRNA level in the para-cancerous tissues relative to normal oral mucosa of the patients whose CK19mRNA expression was not different from those CK19mRNA expression was negative in lymph nodes.Conclusions: 1. The expression of CK19mRNA in the cancerous tissues were higher than that in para-cancerous tissues and normal oral mucosa.2. The expression of CK19mRNA between the para-cancerous tissues and the normal mucosa was not different. 3. The detection of CK19mRNA in lymph nodes was regarded probably as one of the markers for detection of OSCC micrometastasis in lymph nodes. 4. The expression of CK19mRNA in cancerous tissues relative to para-cancerous tissues and normal oral mucosa decreased after micrometastasis appeared in the local lymph nodes.