The treatment of essential fatty acid deficiency (EFAD) in a 17-year-old male following allogeneic bone marrow transplantation is described. His transplant was complicated by gastrointestinal bleeding that precluded the use of enteral feedings. Due to a severe soy allergy, he could not tolerate any intravenous fat emulsions marketed in the US. After months of receiving fat-free parenteral nutrition and intermittent use of enteral feeds, he developed signs and symptoms consistent with EFAD, including a rash and an elevated plasma triene:tetraene ratio of 0.231 (0.013-0.05). After receiving FDA approval, a parenteral fish oil emulsion was administered to provide fat calories and sufficient alpha-linolenic and linoleic acid to correct his EFAD. Therapy was initiated at 0.2 g/kg/day and advanced to 0.67 g/kg/day, providing approximately 45 mg/kg/day of linoleic acid. After 10 days of therapy, his rash disappeared and his triene:tetraene ratio improved to 0.07. By day 17 the ratio normalized to 0.047. This suggests that using a fish oil emulsion with minimal linoleic acid may be safely used as the sole source of fat calories and may be an option to prevent or treat EFAD in subjects allergic to soy that require a parenteral source of fat.