OBJECTIVE To compare tolerance of two sources of isocaloric intake (fructose-glucose-xylitol mixture [FGX] versus glucose) in parenteral nutrition for patients with systemic inflammatory response syndrome (SIRS). METHODS Open, prospective, cohort and randomized study. METHODS Intensive Care Unit. METHODS Two groups of patients admitted in ICU: acute pneumonia with sepsis, and necro-hemorrhagic pancreatitis. Criteria of exclusion were: diabetes, previous hypertriglyceridemia, renal failure with serum creatinine > 3 mg/dL on admission in ICU, or hyperbilirrubinemia > 2.5 mg/dL. Parenteral nutrition (TPN), consisting of 1.4 g AA + Lipids 1.3 g + carbohydrates 4 g/kg/d, (either glucose or FGX at random) was administered. Basal levels and days 1st, 4th and 10th plasma glucose, triglycerides, cholesterol, uric acid were determined, and blood venous gases as well. Capillary glycemia was measured every 6 hours and insulin given if glucose levels rose above 180 mg/dL. METHODS Fisher's exact test; Student t-test; Mann-Whitney test. Data as mean and SD. CONCLUSIONS During 48 months, 119 patients admitted in the ICU (72 with pneumonia and 47 with pancreatitis) were included. In pneumonia, tolerance was similar with both intakes; glycemia was kept at the same level in both, but the amount of insulin given was significantly more in those patients fed on glucose (p < 0.05). Nevertheless, resting blood glucose and triglyceride levels were higher in pancreatitic patients, and more insulin was required. Those on FGX had lower triglyceride plasma levels (p < 0.05) and less insulin was given throughout the study. Glycemia was kept lower though no statistical significance was reached (p < 0.1). No hyperuricemia nor lactic acidosis was found.