The hepatitis B virus (HBV) markers have been studied in 184 household contacts of 110 thalassemic patients and 184 normal individuals matched for age and socioeconomic status with the study subjects. The mean age ( ± SD) in both patients and control subjects was 31.1 ± 13.5 years. HBV infection had occurred in 51.6% of the household contacts and in 32.1% of the control subjects. This difference is highly significant (p < 0.001). The most frequent marker observed was the antihepatitis B core IgG followed by the antihepatitis B surface antibody. It is noteworthy that none of the thalassemic patients infected in the past was seropositive for the hepatitis B surface antigen at the time of the study, whereas its frequency in the general population was 8.1%. The findings indicate that the household contacts of thalassemic patients have a greater seroprevalence for hepatitis B infection. Furthermore, the household contacts of thalassemic patients are infected at a younger age than the control population. The high infection rate with HBV in all groups tested suggests that vaccination should be considered not only for the household contacts of thalassemic patients but possibly for the entire Greek population.