Abnormalities of the tumor-suppressor p53 gene have been discovered in human hepatocellular carcinoma (HCC). It is unclear, however, whether HCC related to chronic viral hepatitis is associated with p53 gene alterations. In this study, we have examined p53 abnormalities in HCC associated with hepatitis C and B virus (HCV and HBV) infections. Tissues from 18 HCC patients from several hospitals throughout the United States were collected (9 were HCV-infected, 5 were HBV-infected, 1 was HCV/HBV-infected, and 3 were non-virus-associated). Immunostaining with monoclonal pAb 1801 revealed expression of p53 protein in tumor-cell nuclei in one HCV-associated HCC, and in no case of HBV-associated HCC, while the nuclei of adjacent hepatocytes were negative. Using Hae III-digestion of chromosomal DNA, mutations at codon 249 were not found in any of 18 HCC tissues studied. Direct sequencing demonstrated a mutated codon 244 and a wild-type codon 249 in the conserved regions (exon 5-8) of p53 gene from the tumor tissue with nuclear p53 expression. By reverse-transcription-polymerase chain reaction (RT-PCR), the expression of p53 mRNA was demonstrated in tumor cells from 10 out of 16 HCC tissues. In conclusion, the specific mutation at codon 249 with G to T transversion was not observed in the HCCs associated with HCV or HBV infections. In HBV or non-virus-associated HCCs studied, no other p53 gene abnormalities were found. A point mutation at codon 244 with G to A transition of p53 gene was detected in only one of 10 HCV-associated HCCs, which suggests that p53 mutations may not play a significant role in HCV- or HBV-associated hepatocarcinogenesis.