Chronic hepatitis B virus (HBV) infection and dietary exposure to aflatoxin B1 (AFB1) are major risk factorsfor hepatocellular carcinoma (HCC). The aim of this study was to evaluate the role of HBV genetic variationand the R249S mutation of the p53 gene, a marker of AFB1-induced HCC, in Thai patients chronically infectedwith HBV. Sixty-five patients with and 89 patients without HCC were included. Viral mutations and R249Smutation were characterized by direct sequencing and restriction fragment length polymorphism (RFLP)in serum samples, respectively. The prevalences of T1753C/A/G and A1762T/G1764A mutations in the basalcore promotor (BCP) region were significantly higher in the HCC group compared to the non-HCC group.R249S mutation was detected in 6.2% and 3.4% of the HCC and non-HCC groups, respectively, which was notsignificantly different. By multiple logistic regression analysis, the presence of A1762T/G1764A mutations wasindependently associated with the risk of HCC in Thai patients.