This study was designed to determine the amount of linoleic acid required to prevent essential fatty acid deficiency in premature infants. This was achieved by infusing 1 g intravenous lipid.kg-1.d-1 over 18-20 h beginning on day 2 and increasing by 0.5 g.kg-1.d-1 to a maximum of 3 g.kg-1.d-1. The actual mean amounts of linoleic acid administered (mg/kg) were 613 on day 2, 767 on days 3 and 4, 862 on day 5, and 1062 on day 6. None of the neonates managed in this fashion showed a high triene-tetraene ratio on days 3 or 7 (in contrast to control subjects, 80% whom were abnormal). Plasma triglycerides and nonesterified fatty acids (NEFAs) increased during the infusions but not to concentrations indicative of fat intolerance. The rise in NEFAs was associated with evidence of bilirubin displacement from circulating albumin but this occurred to only a modest degree.