A cross-sectional study of 165 school-age children who had no history of HBV vaccination was carried out in a low socioeconomic community of Din-Daeng, Bangkok. Blood specimens were collected for determination of HBV seromarkers (HBsAg, Anti-HBs and Anti-HBc) by EIA commercial kits. The results showed that the prevalence of HBV seromarkers was 24.85%, the HBsAg carrier rate was 3.64%, the anti-HBs positive rate was 15.15%, and the prevalence of only anti-HBc was 6.06%. To investigate factors associated with the positivity of HBV seromarkers, children were divided into two groups--the first group consisted of 41 children with HBV seromarkers and the second consisted of 124 children without HBV seromarkers. The study variables between the two groups were compared and analysed. The results revealed that factors associated with HBV positivity were (a) child factors: child's age, child's sex, ear piercing in female, sharing blade during haircutting, contact wound from other persons, using wares with other persons, searching things in garbage, and (b) family factors: older parent, low education in parent, low family income per month, low parent's knowledge and attitude about HBV infection and vaccination, (P < 0.05). After using stepwise regression analysis, the factor of ear piercing in female was only one significant variable.