It has been known that the incidence of p53 mutation is very rare in HBX-positive primary human hepatocellular carcinoma (HCC) tissues. The frequency of p53 mutation, however, in established cell lines with integrated HBV DNA and/or HBX has not been well studied. To know p53 mutational frequency, and to investigate whether the presence of HBX DNA sequence correlates with the absence of p53 mutation in the established HCC cell lines, we studied the p53 mutation and the presence of HBX sequence in 12 recently characterized HCC cell lines. As a result, all 12 (100%) lines showed mutation in the p53 gene. Three (25%) cell lines had transversion of codon 215 while no mutation of codon 249 was found. In contrast with previous reports, although HBX DNA was present in 11 cell lines, p53 mutation had occurred, indicating that the presence of HBX viral DNA does not correlate with a lack of p53 mutation in established HCC cell lines. Our results suggest that the frequency of p53 mutation is extremely high even in HBX DNA positive HCC cell lines.