Screening of total IgE in 2814 cord blood samples was analysed by Phadebas IgE PRIST in 2 1-year birth cohorts (1983-1984 and 1985-1986) in Denmark (n = 1189 + 1625). 48.6% of the sera contained less IgE than the detection limit 0.1 kU/l. Cord blood IgE values greater than or equal to 0.5 kU/l were regarded as elevated. 13.2% of the sera contained at least 0.5 kU/l of IgE, with a significant preponderance in boys. Geometric mean cord blood IgE was 0.13 kU/l and 0.12 kU/l, respectively. Geometric mean cord blood IgE was significantly higher in boys. A significant seasonal variation with lowest IgE values in the autumn was found. No correlation between cord blood IgE and birth weight or gestational age was demonstrated. Only few newborns had cord blood IgA values greater than 0.014 g/l, calculated as geometric mean cord blood IgA + 2 SD among children with no detectable cord blood IgE, indicating infrequent contamination with maternal blood.