Serum IgE was estimated in 226 healthy children aged 0-14 years without obvious atropic disease in their first degree relatives. A paper disc radioimmunoassay technique (PRIST) was used. A number of criteria for selection of cases were established. This led to the exclusion of forty-two potentially atopic children. The remaining group of 184 children is considered representative of normal children and may therefore be used for reference purposes. The IgE levels were found to be lower than in previous investigations, and this is attributed to the refined technique and the method of selection.