Serum IgE levels and the prevalence of certain atopic diseases have been studied in 819 individuals in 176 white families living in central Saskatchewan and in 275 individuals in 58 Metis families living in northern Saskatchewan. The geometric mean serum IgE level in the white community (81.3) u/ml) was lower than that in the Metis community (275.4 u/ml). The prevalence of asthma, eczema and urticaria was greater in the white than in the Metis community and contrasted with the increased prevalence of helminth infestation as well as of other untreated viral and bacterial diseases in the Metis community. It is suggested that atopic disease is the price paid by some members of the white community for their relative freedom from diseases due to viruses, bacteria and helminths.