To investigate the effects of a dam’s dietary elaidic acid (EA) intake during pregnancy and lactation on the fatty acid composition of plasma, erythrocyte membrane, and brain in rat pups, we fed two groups of dams either a soybean oil diet (SOD) or a shortening diet (SHD) containing soybean oil (10%) or shortening (10%), respectively. Although EA was not detected in the SOD, EA accounted for 25.3% of all fatty acid content in the SHD. On day 8 after birth, the EA levels in the stomach, plasma, and erythrocyte membrane of pups nursed by the dams fed the SHD were %, %, and %, respectively. Although on day 8 after birth the EA level of the brains of pups nursed by SHD-fed dams was %, EA was not detected on day 21 or day 82 after birth. These results suggest that EA intake during pregnancy and lactation supplies EA to plasma, remains in the erythrocyte membrane of pups, and moves into the brain in early infancy.