Annexin I plays an important role in the process of keratinization as a compont of the cornified envelope of skin epithelium. The effect of annexin I on the terminal ifferentiation of normal human oral keratinocyte(NHOK) have remained to be defined. To understand the role of annexin I on the terminal differentiaiton of NHOK, NHOK and NHEK cells were primarily cultured in KBM bullet kit. When the cells reached confluence, terminal differentiation was induced by switching the medium to KGM bullet kit containing 1.2mM Ca2+. Preconfluency of NHOK under 0.05mM Ca++ conc as control group was used. The cells was examined with inverted microscope. Under 0.05mM Ca++ conc(Precon, Postcon), and 1.2mM Ca++ conc(Postcon), RT-PCR for annexin I mRNA measurement, and immunoblotting for annexin I protein measurements in triplicate, respectively. The purpose of this study were to study differential mRNA & protein expression of annexin I between NHOK & NHEK by using RT-PCR & immunoslot blotting during terminal differentiation, and to apply these results to study a role of annexin I on epithelial differentiation of oral mucosal diseases in the future. Cultured NHEK showed larger area of cellular stratification than cultured NHOK in 1.2mM Ca ++ concentration. Annexin I mRNA and protein expression of cultured NHOK showed higher than that of cultured NHEK in higher calcium concentration. Annexin I mRNA and protein expression of cultured NHOK showed about 2-2.7 fold higher in 1.2mM Ca++ conc. than in 0.05mM Ca++ conc. Although annexin I was involved in the terminal differentiation of cultured NHOK & NHEK in higher calcium concentration, annexin I play an important role in the terminal differentiation of cultured NHOK in higher calcium concentration. From the aboving results, It was suggested that annexin I would play an important role in the terminal differentiation of NHOK in higher calcium, which be helpful to study epithelial differentiation of oral mucosal diseases.