126 children of 102 hepatitis B surface antigen (HBsAg) carrier mothers were delivered at Hammersmith Hospital and Queen Charlotte's Maternity Hospital, between 1971 and mid-1978. Blood tests on 110 of these children showed that 8 out of the 18 with Chinese mothers, but only 6 out of the 92 other children, have become HBsAg positive. The presence of maternal hepatitis B e antigen (HBeAg) is also significantly correlated with transmission of HBsAg to the children. The management of children whose mothers are carriers is discussed.