The predictive value of cord blood IgE (cIgE) for atopy and related disorders was investigated. Samples were collected from 792 infants delivered consecutively at the National University Hospital in Reykjavík in 1987. The concentration of IgE, but not that of IgA, was found to increase with increasing gestational age at birth. There was no correlation between IgE and IgA levels in individual samples. At the age of 18-23 months 180 of these children were studied for manifestations of allergy and related disorders. Included were all available infants with detectable (> or = 0.23 kU/L) cIgE. However, infants born by Cesarean section or with IgA exceeding 10 mg/L were excluded because of potential contamination with maternal blood. The clinical evaluation was made without knowledge of the IgE levels. Sixty-six of the 180 participants (36.6%) were judged to have had definite allergic manifestations. However, no striking correlation was found between allergic symptoms and cIgE levels in this study, nor did high levels of IgE add significantly to the predictive value of family history. Children with atopic features had more frequently been affected by otitis media. Unexpectedly, infants with intermediate cIgE levels (0.2-0.6 kU/L) were significantly less affected by otitis media than children with unmeasurable (< 0.2 kU/L) or high (> or = 0.7 kU/L) cIgE levels. It is concluded that cord blood IgE can not be used to predict allergic manifestations in children under the age of 2 years.