Since oral keratinocytes represent the natmal target for HPV(human papill omavi ruses) infecti on, HPV infection may be involved il1 the developmel1t of oral SCC. Through compaJ'ing the morph이 ogic featw-es of NHOK to 다fOK accorcling to calcium concentration by TEM, immortali zed oral keratinocytes(IHOK) transfected by E6/E7 gene of HPV 16 have been gained wide acceptance as a model system for HPV-linkecl oral carcinogenesis. The purpose of this study were to exami ned the ultrastructural fcaturcs of culturcd NHOK, IHOK, and HN4 oral squamous cell CaJ‘CI noma celJ line, and to apply these results to oral carcinogenesis in the future, Prima:rily cul tlU'ed NHOK, IHOK ++ and HN 4 cell line which were cu ltu red under 015 and 12mM CaTT of 1ιBM bulJet kit For tra nsmission electronmi crosco py(TEM). under preconfluency‘ and after 3 days of postconfluency uncler 1.2mM Ca ++‘ cultured NHOK IHOK, and HN4 cell line were immediately fixed in 2, 0% gluta:raldehyde in O.lM cacodylate buffer(pH 7, 4) at 40C 1'01' 1h TEM of cultured NHOK under 1. 2mM Ca ++ showed increased tonofi laments‘ and vaculated ovoid cells wi th cornifi ed envelope, whi le cultured IHOK showed prominent microvilli , unilateral desmosome in microvillus‘ and tonof t!amen ts Under high calcium cu ltured IHOK showed less tonofilaments than that of cultured NHOK, while cu ltu red lHOK a nd HN 4 cell lines showed more increased desmosomes under high calclUm It suggested that the ultrast ru ctura l cha nges of cultured IHOK would be accepted as the morphologic changes of intermediate stage aJl10ng oral carci nogenesis ,