To evaluate the effectiveness of hepatitis B virus (HBV) vaccination of household contacts of HBV carriers in Tulkarm district, Palestine, quantitative hepatitis B surface (anti-HBs) antibody response in 161 household contacts was measured after vaccination. A seroprotective anti-HBs response (titre > or = 10 IU/L) was elicited in all vaccinated subjects. Of these 2.5% had titres of 10-99 IU/L, 61.5% 100-999 IU/L and 36.0% > or = 1000 IU/L. The number of vaccination doses had no effect on the achievement of seroprotection. HBV infection was demonstrated in 13 cases and their anti-HBV titres were in the range 25-350 IU/L.