Abstract. A group of 207 healthy non-atopic children 0–14 years of age without any known family history of atopic disease was selected for a study of the relation between serum IgE levels and the occurrence of atopic manifestations during an observation period of 18 months; 206 fullfilled the study. Serum IgE was measured by a direct radioimmuno-logical sandwich technique (PRIST1). At the follow-up 28 of 32 with an initial IgE level greater than one standard deviation above the mean for the age continued to show a high level (87.5%). The total concordance was 81.1%. Atopic or probable atopic diseases had developed in 75.0% of children 0–1 year of age with an initial IgE above +1 S.D., but in only 6.4 % of those from the same age group with a lower initial IgE. Even among children 2–14 years old, it was noticed that a high IgE level was predictive of the subsequent development of atopic disease. Otitis media was more frequent among children with an initially elevated IgE level than among the rest of the children. Determination of serum IgE with the PRIST-technique has been shown to provide a valuable means for predicting future atopic manifestations and may be used as a screening procedure especially in children of atopic parents.