Some studies have already investigated the effect of a maternal 18:3n-3-rich diet on newborn fatty acid composition. For example, Bazinet et al.(12) showed that piglets suckling sows consuming an 18:3n-3-rich diet had 54% more 22:6n-3 in their liver and 24% more 22:6n-3 in their brain than control piglets at 14d of age. Farmer & Petit(13) also demonstrated that a maternal 18:3n-3-rich diet increased the percentage of 22:6n-3 (1·2 times more than control) in piglet brain at 1d of age. Moreover, supplemen- tation of the maternal diet with LSO slightly increased the proportions of 20:5n-3 and 22:6n-3 in piglet plasma at birth(14). In parallel, in human subjects, maternal 18:3n-3 supplementation during pregnancy increased the proportion of 20:5n-3 by twofold in newborn plasma at birth(15). These studies clearly confirm that 18:3n-3 supplementation can increase LC-PUFA status in the newborn. However, only one time point has been studied after birth. The main objective of our experiment was to investigate, in sows and piglets, the effect of maternal LSO intake on the fatty acid composition of the sow plasma and placenta and on the fatty acid composition of different tissues of the newborn before any suckling. The effect of maternal LSO intake on the evolution of the fatty acid composition of sow milk and piglet tissues at different time points during the suckling period was also established