Changes in plasma zinc levels were studied in 11 pediatric surgical patients treated with total parenteral nutrition. Plasma copper levels were also determined in some patients. In three patients plasma zinc fell to a very low level during long-term total parenteral nutrition, and a syndrome of zinc deficiency developed characterized by dermatitis, alpecia, and enterocolitis with striking response to intravenous zinc therapy. In contrast, plasma zinc levels in the patients with short-term total parenteral nutrition remained in the normal range during the present study. This suggests that one of the mechanisms of zinc deficiency during total parenteral nutrition is insufficient amount of zinc in the nutritional solutions for long-term use, especially for older children. Symptoms of the zinc deficiency also occurred in these patients during the anabolic phase, suggesting that tissue demand for zinc may be increased at that time. Therefore, zinc should be included, on a regular basis, in all parenteral nutritional solutions in amounts sufficient to meet estimated needs for growth and tissue repair.