INTRODUCTION: Although hepatitis B virus infection is well-described, the additional risk posed by oral bleeding in individuals with chronic hepatitis B virus infection has not been determined. This study aimed to determine the quantity of hepatitis B virus in the saliva of carriers in Japan, as a means of understanding the potential risk for horizontal transmission. METHODS: Saliva samples from 48 confirmed hepatitis B virus carriers were included in the analysis. Hepatitis B virus concentrations and the presence of occult blood as periodontal disease were evaluated in each sample. RESULTS: Hepatitis B surface antigen was identified in 46 of the 48 samples (98%), with hepatitis B virus DNA identified in 19 of the 48 saliva samples (40%). Occult blood was detected in 32 (67%) samples with the prevalence increasing as a function of age (r = 0.413; P = 0.003). There was a significantly positive correlation between hepatitis B virus DNA levels in the serum and saliva specimens (r = 0.895; P < 0.001). CONCLUSIONS: Occult blood in saliva was detected in most participants. The detection of hepatitis B virus DNA correlated positively with hepatitis B virus in the serum and occult blood in the saliva. Therefore, improved care of periodontal disease among older people is important for preventing horizontal transmission of hepatitis B virus.