Background: Vietnam is located in the endemic region of hepatitis B virus (HBV) infection, but no data of occult HBV infection was reported at present. Objectives: To investigate the prevalence of occult HBV infection in different ethnics of people and generations. Subjects and method: 80 voluteers with HbsAg negative from five different ethnics: Kinh, Tay, Mong, Giay and Dao in a Chino \ufffd?Vietnamses border province (Lao Cai) were enrolled in the study. After HBV-DNA was extracted, nested PCR of S gene and of Core-promoter/Pre-core region were used to detect HBV-DNA. Specifying nucleotide sequence was confirmed by direct sequencing. Results:The prevalence of occult HBV infection in population study was very high 73/80 (91,3%) by nested PCR of Core-promoter/Pre-core, significantly more sensitive than nested PCR of S gene (26,3%) (p<0,0001). The prevalence of occult HBV infection was notdifferent between ethnics of people or between children, adults. Conclusion: Occult HBV infection in Vietnamese is very common; however, nationwide further studies should be carried out to confirm this preliminary results and evaluate the impact of occult HBV infection in Vietnam.