1.1. Phospholipid, total and free cholesterol, triglyceride, and nonesterified fatty acids were determined in maternal serum, fetal serum, and placental tissue obtained at delivery. Total lipid and water contents were also determined on the placentas.2.2. Normal pregnant patients (12) were compared to toxemic patients (10). The toxemic group consisted of 4 eclamptic and 6 severe pre-eclamptic patients.3.3. The only significant difference between the two groups was the triglyceride content of the placenta, which is significantly elevated in toxemia.4.4. Correlation coefficients were calculated between each lipid fraction in maternal serum and the corresponding measurement in fetal serum to see if high and low values in maternal serum corresponded to high and low values in fetal serum. No significant correlations were obtained. This suggests that simple diffusion of lipid fractions from maternal serum to fetal serum does not occur.5.5. Significant positive correlations between the free cholesterol content and the phospholipid content were obtained in maternal serum, fetal serum, and placental tissue in control patients. In the toxemic patients, only in maternal serum was a significant correlation obtained.6.6. Significant positive correlations between the total cholesterol content and the phospholipid content were obtained in maternal serum and fetal serum in control patients. Toxemic patients showed a significant correlation only in maternal serum.7.7. In normal pregnancy certain factors are responsible for the positive relationship between cholesterol and phospholipid levels in fetal serum and placentas. In toxemia of pregnancy these factors are altered.