Dietary n-3 PUFA have many beneficial effects on cell and tissue function and on human health. In mammals the n-3 essential fatty acid alpha-linolenic acid (ALNA) can be converted into longer-chain (LC) n-3 PUFA such as EPA and DHA via a series of desaturase and elongase enzymes that are mainly active in the liver. Human studies have identified that males and females appear to differ in their ability to synthesise EPA and DHA from ALNA, with associated differences in circulating concentrations. Based on studies of women using the contraceptive pill or hormone-replacement therapy and of trans-sexual subjects it is suggested that sex hormones play a role in these differences. The rat has been used to investigate gender differences in n-3 PUFA status since this model allows greater dietary control than is possible in human subjects. Like human subjects, female rats have higher plasma DHA concentrations than males. Rats also respond to increased dietary ALNA in a way that is comparable with available human data. The concentrations of LC n-3 PUFA in rat plasma and tissues are positively associated with circulating concentrations of oestradiol and progesterone and negatively associated with circulating concentrations of testosterone. These findings suggest that sex hormones act to modify plasma and tissue n-3 PUFA content, possibly by altering the expression of desaturase and elongase enzymes in the liver, which is currently under investigation.