We assessed the long-term immunity to hepatitis B among 242 Egyptian children aged 6-12 years who had received a full vaccination course in infancy, and investigated the factors associated with immunity. Only 39.4% of the children had protective (> or = 10 lU/L) hepatitis B surface antibody levels (HBsAb). This proportion decreased with age but the decrease was not statistically significant. The mean level of HBsAb decreased significantly with increasing age (P = 0.026). A significant negative correlation was found between current age and HBsAb levels (r = -0.31, P = 0.041). Age and weight-for-age were found to be significant predictors of non-protective HBsAb levels.