Abstract. Human papilloma virus (HPV) has been recently proposed to be implicated in the development of head and neck squamous cell carcinoma (HNSCC) in patients without cancer risk. We examined the expression of HPV16/18 E6/ E7 in 71 cases of HNSCCs and investigated abnormalities of the p53 gene in 62 of these 71 cases. Expression of HPV16 E6/E7 was observed in 11 of the 71 cases (15.5%), while expression of HPV18 E6/E7 was not observed in any of the cases. Most of the HPV16 E6/E7-positive cases were histopathologically characterized by their verrucous or papillary structure and koilocytosis of the adjacent mucosa. There was no clear relationship between expression of HPV16 E6/E7 and tumor stage, prognosis or the positive rate of p53 abnormality. These results suggest that approximately 15% of HNSCCs are caused by HPV16 infection and the subsequent constitutive expression of E6 and E7, and that some HPV-initiated tumors lose their original characteristics during tumor progression.