Fatty acid patterns were determined for maternal and cord sera from normal and preeclamptic pregnancies using gas liquid chromatography. Ten normal and 11 preeclamptic maternal sera were used; 6 preeclamptic and 6 normal cord sera were measured. Fatty acid patterns were measured in the nonesterified fatty acids (NEFA), the triglycerides (TG), the cholesterol esters (CE), and the phospholipids (PL). Preeclampsia showed significant differences in the essential fatty acid patterns in the maternal and cord sera compared to normal pregnancy. Oleic acid, an early indicator of essential fatty acid deficiency, made up a significantly greater proportion of preeclamptic cord blood NEFA, TG, and PL than in normal cord blood. Abnormalities in essential fatty acid patterns may be associated with decreased prostacyclin production and dysmaturity which may be seen with preeclampsia.