AIM: To determine the prevalence of hepatitis B in Nahavand and evaluate the HBsAg positive prevalence in families with a member who was confirmed to have HBV infection. METHODS: This study was performed in two phases. In the first phase, 1 824 subjects in Nahavand city were selected. The interviewers visited the houses of chosen families to fill the questionnaire and take the blood samples. All subjects signed an informed consent before interviews and blood sampling. The samples were evaluated for HBV virologic markers. In the second phase, 115 HBsAg-positive cases were enrolled and evaluated for HBV virologic markers. RESULTS: The prevalence of positive HBsAg in Nahavand was 2.3%. The most frequent relatives of index cases were sons and daughters (32.2% and 23.5% respectively). Twelve (11%) of all family members were HBsAg positive. Fifty (56.2%) were isolated HBsAb positive and only one person (2,5%) was isolated HBcAb positive. The higher rates of HBsAg marker were detected in the brothers (1-25%) and fathers (1-12.5%). The infection rate in husbands and wives of index cases was 10%. Only two (16.7%) of all HBsAg-positive participants reported previous HBV vaccination. CONCLUSION: The prevalence of intra-familial HBV infection is lower in Nahavand of Iran compared to other studies. More attention should be paid to HBV vaccination and risk-lowering activities. METHODS: This study was performed in two phases. In the first phase, 1 824 subjects in Nahavand All subjects signed fill the questionnaire and take the blood samples. All subjects signed fill in the questionnaire and take the blood samples. All subjects signed an informed consent before interviews and blood sampling. In the second phase, 115 HBsAg RESULTS: The prevalence of positive HBsAg in Nahavand was 2.3%. The most frequent relatives of index cases were sons and daughters (32.2% and 23.5% respectively). Twelve (11%) of all family members were HBsAg positive. Fifty (56.2%) were isolated HBsAb positive and only one person (2,5%) was isolated HBcAb positive. The higher rates of HBsAg marker were detected in the The infection rate of husbands and wives of index cases was 10%. Only two (16.7%) of all HBsAg-positive subjects reported previous previous HBV vaccinations. CONCLUSION: The (1 - 12.5%) and fathers prevalence of intra-familial HBV infection is lower in Nahavand of Iran compared to other studies. More attention should be paid to HBV vaccination and risk-lowering activities.