Oral squamous cell carcinoma is the 1st most common malignancy in oral and maxillofacial area. HPV 16 has been strongly linked to progression of cervical carcinoma. E6 and E7 as a small DNA virus encoding two major oncoproteins of HPV 16 can act together to produce efficient immortalization of primary human epithelial cells. Thus it is important to pursue the development of Immortalized human oral keratinocyte(IHOK) culture model which could be related to the pathogenesis of oral squamous cell carcinoma. If we establish IHOK transfected by E6/E7 genes, IHOK will be accepted as a model system for HPV-linked oral carcinogenesis. The purpose of this study were to culture primary normal human oral keratinocyte(NHOK), and to establish IHOK for studying oral carcinogenesis in the future. NHOK was primarily cultured under normal culture condition, and transformed into IHOK by transfection of E6/E7 genes. After 100 passages depend on Ca++ condition, cultured IHOK was confirmed by growth curve, cornified cell envelope measurement, TGase 1activity, mRNA detection, tumorogenecity and anchorage independence assay. After 100 passages, cultured IHOK showed most basal cell and monolayer of polyhedral cells under 0.15mM Ca++, and small area of stratification and flattened epithelial cells with irregular border under 1.2mM Ca++. The cultured IHOK showed relatively resistant growth under high calcium condition. The E6/E7 mRNA was detected in cultured IHOK by RT-PCR. During the terminal differentiation in cultured IHOK, increased insoluble cornified cell envelope formation was accompanied with induction of TGase 1 activity. But the cultured IHOK showed less CEM and TGase 1 activity than those of cultured NHOK. Cultured IHOK showed non-tumorogenecity, but slight anchorage independence. We had developed a technique to transform NHOK into IHOK by transfection of E6/E7 genes. Cultured IHOK was established as intermediate stage cell to study the pathogenesis of human oral squamous cell carcinoma.