The fatty acid composition of umbilical cord serum phospholipids was investigated by gas chromatography in 33 infants with allergic and 35 babies of non-allergic mothers. The relative levels of the linoleic acid metabolites C20:3, arachidonic acid (AA, C20:4) and C22:4n-6, and two alpha-linolenic acid metabolites, i.e. eicosapentaenoic acid (EPA, 20:5) and docosahexaenoic acid (DHA, C22:6) were significantly higher in infants of allergic mothers than in non-allergic mothers (all p < 0.05). Furthermore, an altered proportional relationship between the various fatty acids in n-6 series fatty acids and between n-3 and n-6 series fatty acids was present already at birth in infants who developed allergic disease during their first 6 years of life. These observations cannot be employed for the prediction of allergy, however, as the individual variations were considerable.