Cord serum IgE levels were examined in 101 newborn infants of atopic parents, and reviewed at the ages of 3, 6, 9, 12, 15, 18, 21 and 24 months, in order to determine any relation with signs and symptoms of allergic rhinitis, bronchial asthma, atopic dermatitis, urticaria and food allergy. Cord blood IgE levels were 1.06 +/- 1.02 U/ml in the group of infants who developed atopic disease, and 0.34 +/- 0.79 U/ml in the group of infants who did not develop atopy (P less than 0.001). In the breast-fed group 37.5% of the infants with cord blood IgE more than 0.8 U/ml and 11.5% with IgE below 0.8 U/ml had atopic disease. In the soy-fed group 33.3% of the infants with cord blood IgE more than 0.8 U/ml and 15.8% with cord blood IgE less than 0.8 U/ml developed atopy. Ninety percent of the cow's milk-fed infants with cord blood IgE above 0.8 U/ml and 16% with cord blood IgE below 0.8 U/ml showed atopy during the follow-up period. No correlation was found between the IgE levels in maternal and respective cord blood.