The influence of the mother's consumption of cows' milk and hens' egg on the immune response (IgE, IgG) in the mother and foetus was studied in 165 pregnant women with atopical respiratory disease with an allergy to pollen and/or animal dander. The women were randomly allocated to four diets ranging from a diet free from hens' egg and cows' milk to a diet containing intake of one egg and one litre of milk daily during the third trimester. No significant differences in cord blood IgE levels were noted in spite of differences in maternal diet, and no specific IgE antibodies to ovalbumin, ovomucoid and betalatoglobulin were found in the cord blood. The mother's IgG antibody concentrations to ovalbumin, ovomucoid and betalactoglobulin were influenced by her diet, but cord blood IgG antibody levels to the selected food allergens were unaffected. The data presented on the IgE and IgG antibody levels to ovalbumin, ovomucoid and betalactoglobulin in cord blood suggest that changes in maternal diet during the last trimester of pregnancy in order to prevent atopic sensitization in utero are less likely to affect the foetus than previously supposed.