1. EFA deficiency is associated with the impairment of prostaglandin E synthesis, which is reflected by the decrease of the urinary excretion of PGE-M. 2. Excessive administration of Intralipid results in increase of the relative concentrations of linoleic acid content in plasma, RBC, and tissues with a concomitant decrease of its higher homologue, arachidonic acid. These changes are associated with diminished PGE-M excretion similar to that seen in EFA deficiency. Further investigation is needed into the pathophysiologic consequences of EFA deficiency and the excessive administration of linoleic acid since both are associated with altered prostaglandin biosynthesis and turnover in the new-born infant, particularly among those stressed low birth weight infants whose nutritional status and management are an indication for these modes of therapy.