An assessment was made of the blood lipid pattern in a group of patients in critical situations subjected to T.P.N. with a mixed calorie intake (sugars, lipids, amino acids). It was found that the pronounced previous deficiency was corrected in a significantly shorter period, and that despite the large load on calories in the form of fats there were no changes worthy of note in the body fluids. Serial determination of lipoproteins before, during and after T.P.N. substantiated the clinical findings. Lab checks, within the limits set by intuitive variations, did not reveal alterations with a pathological meaning, for the very reason that they were not linked to organic enzyme and hormone deficiencies, but were positive changes attributable to the temporary exogenous input.