Total nutrient admixture (TNA) combines amino acids, lipids, and glucose in a single bottle for continuous parenteral use. This cost-effective and easily administered solution is now available for use in neonates. The present study was performed to assess the metabolism of fat administered as TNA in sick neonates as reflected by serum free fatty acid (FFA) and triglyceride (TG) levels. During a 6-month period, TG and FFA levels were monitored in all infants receiving TNA. Levels were measured within 24 hours of a change in lipid dose and then weekly when maximum intake (about 2 g/kg/day) was achieved. Sixty-nine TG and 58 FFA levels were obtained from 42 neonates who at the time of sampling were receiving 2 g/kg/day or more of parenteral lipid. Ninety-one percent of TG levels were less than or equal to 200 mg/dL. Ninety-six percent of FFA levels were less than or equal to 2000 mumol/L. A weak but statistically significant correlation was noted between TG and FFA levels with a correlation coefficient of 0.54. In conclusion, although the range of FFA and TG levels obtained from sick neonates on TNA therapy is relatively wide, these levels are comparable to those reported in the literature for infants receiving standard intravenous lipid infusions.