Despite Department of Health recommendations, universal antenatal testing for hepatitis B virus (HBV) is not performed throughout Scotland. We describe the evaluation of an assay to document past or present infection with HBV, by identifying maternal antibody in routine Guthrie dried neonatal blood spot samples taken when infants are 7 days old. A modified haemagglutination assay to detect antibody to hepatitis B core antigen (CORECELL, Green Cross) was validated and found to be 79% sensitive (44/56) and 100% (105/105) specific when used with dried blood spot samples made from panels of serum of known reactivity. Ninety-three percent (13/14) of HBV carriers were CORECELL positive. Sixty-six (0.5%) of 14044 routine Guthrie samples taken from babies born in Scotland from June August 1992 were CORECELL positive indicating past or present maternal infection with HBV. A cross-sectional survey would document the maternity hospitals where universal antenatal hepatitis B screening should be urgently established.