The essential fatty acid (EFA) status of neonates was compared with that of their mothers by determining the fatty acid compositions of phospholipids (PL), isolated from umbilical arterial and venous tissue, blood cells (BC) and plasma, from maternal venous plasma and BC, and from non-infarcted placental tissue. The PL of umbilical arterial tissue (efferent fetal vessels) contained fewer fatty acids of the (n-6) family and more of the (n-9) family than umbilical venous tissue (afferent fetal vessel). The relative amounts of (n-6) and (n-3) fatty acids were less in arterial than in venous plasma. Mead acid, 20:3(n-9), the presence of which indicates a poor EFA status, was 5 times higher in the efferent than in afferent cord vessels. In neonatal plasma and BC it was twice as high as compared with maternal levels. In general, the fatty acid composition of the placenta PL showed a comparable pattern as neonatal venous plasma PL. These findings demonstrate that the biochemical EFA status of neonates after a normal pregnancy is not optimal. The significant correlations between neonatal and maternal EFAs indicate that the neonatal EFA status depends on the EFA content of the maternal diet.