A total of 848 household contacts of 285 hepatitis B surface antigen (HBsAg) chronic carriers were included in a prospective study. Of the total number of contacts negative for hepatitis B virus (HBV) markers at baseline, 330 relatives of 145 HBsAg carriers were observed over a mean period of 20.1 months. Among all household contacts, 284 (33.5%) were found positive for at least one HBV marker. The prevalence of HBV markers was significantly higher among the contacts of more than one HBsAg carrier (75.9%) than among those with only one (26.0%) (P less than .001). The presence of hepatitis B e antigen (HBeAg), specific HBV-DNA polymerase (HBV-DNAp), HBV-DNA, and polymerized human serum albumin (pHSA-R) in the index case was associated with a significantly higher incidence of HBV markers among household contacts. During the follow-up, the number of household contacts initially negative for HBV markers who became infected was found to be in direct relation to the presence of HBeAg, HBV-DNAp, HBV-DNA and pHSA-R in the index case.