The clinical and biochemical features of essential fatty acid deficiency are described in an infant with gastroschisis who required long-term (6 mo) parenteral nutrition. The deficiency responded to therapy with Intralipid, topical sunflower oil, and breast milk. In a prospective study of three infants with gastroschisis, biochemical essential fatty acid deficiency developed in each during the first week of lipid-free parenteral nutrition; clinical signs of the deficiency were absent. The biochemical features were progressive in the one patient followed for 19 days, and were associated with a decrease in weight gain. Both the deficiency and weight gain were corrected by Intralipid. Biochemical essential fatty acid deficiency did not develop in three other gastroschisis infants who were given prophylactic Intralipid (two patients) or topical sunflower oil (one patient). We conclude that all infants on parenteral nutrition should receive a source of linoleic acid to prevent essential fatty acid deficiency.