In a prospective study, with the objective of determining the metabolic profile, response to nutrient supply, and role of nutritional and metabolic assessment parameters in children admitted to a pediatric ICU, 11 patients in the age group 2-12 were studied. The assessment was carried out during the first 72 hours of admission, and again seven days later, and included the following parameters; caloric supply; nitrogen supply; prealbumin serum level; urinary urea nitrogen; nitrogen balance and creatinine-height index. The evolution of the parameters in the two stages of the study showed the following results: The urinary urea nitrogen median value at admission was 7.5 g/m2 of corporeal surface, and did not present significant changes seven days later. There was a significant increase in caloric supply from 42.9 to 70.3 kcal/kg, and in nitrogen supply, from 4.7 to 10.2 g/m2 of corporeal surface p 0.01. The level of nitrogen balance rose from -5.6 to 2.5 g/24 h (p < 0.03), and that of prealbumin, from 16.7 to 26.3 mg/dl (p < 0.03). There was a significant reduction in the creatinine-height index, from 86.2 percent to 55.0 percent p 0.01. The magnitude of urinary urea nitrogen excretion at admission varied 2.5-13.8 g/m2 of corporeal surface. Based on this parameter, it was not possible to establish a characteristic metabolic profile for the conditions studied. Notwithstanding an increase in the protein and caloric supply, prealbumin level and nitrogen balance observed in the second stage of the study, the patients lost muscle mass and entered into a malnutrition process, probably due to intense protein catabolism and the poor response to nutrition supply that occurs in metabolic stress.