In view of the importance of long-chain polyunsaturated fatty acids (LCP) for growth and development of fetal and infant neural tissue, the influence of the dietary n-3 and n-6 LCP intake on the LCP status of forty-three preterm infants (birth weight <1800 g) was studied. Thirty-one formula-fed infants were randomly assigned to receive a conventional formula lacking LCP (n 16), or an 22:6n-3- and 20:4n-6-enriched formula (n 15); twelve infants received their own mother's breast milk. Fatty acid compositions of plasma and erythrocyte (RBC) phospholipids (PL) were determined in umbilical venous blood, in weekly postnatal samples until day 35 of life and, for the formula-fed infants, at 3 months of corrected age. Both in plasma (P <0.001) and RBC (P <0.01) FL, the changes with time until day 35 for 22:6n-3 and 20:4n-6 in the two groups of formula-fed infants were significantly different, with higher values, comparable with those of human-milk-fed infants, in the LCP-enriched-formula group. At 3 months of corrected age, differences between the two formula-fed groups were even more pronounced. In conclusion, adding 22:6n-3 and 20:4n-6 to artificial formulas in balanced ratios and in amounts similar to those found in preterm human milk raises both the 22:6n-3 and the 20:4n-6 status of formulated preterm infants to values found for human-milk-fed preterm infants. Additional studies are necessary to evaluate the potentially favourable effects of this combined addition on the neurodevelopmental outcome of preterm infants.