During a study to evaluate the effect of a safflower oil emulsion on essential fatty acid status during parenteral nutrition, we also measured plasma triglycerides and plasma free fatty acids (FFA) in a group of preterm infants. Subjects received 0.34 g/kg (group 1) or 0.68 g/kg (group 2) of lipid daily for 5 days. Essential fatty acid status remained normal in both groups, but the changes in plasma triglycerides were greater (p less than 0.025), and hypertriglyceridemia was somewhat more common (p = 0.06) in group 2 than in group 1. Plasma FFA did not differ in either treatment group. However, postinfusion FFA were greater (p less than 0.05) and FFA uptake was less (p less than 0.05) in infants at less than 32 than at 32-34 weeks gestation, but in no instance did postinfusion FFA exceed an FFA/albumin ratio of 6:1. In addition, triglyceride and FFA uptake did not improve during the study, but the changes in plasma triglycerides and FFA were greater (p less than 0.05) at the end than at the beginning of the study.