Metabolic and energetic responses to intravenous infusion of Aminosol (Aminosol-glucose, Vitrum, Stockholm) were studied in 7 pre-term newborn infants. Aminosol caused a 10-percent mean rise in the metabolic rate. The average cumulative calorigenic response to the nutritive solution was found to be 13.4% of the basal heat production and 9.7% of the calories infused. The proportion of glucose and amino acid oxydation markedly increased, while a simultaneous decrease in utilization of fat could be observed. At the same time a considerable increase in plasma concentration of glucose and α-amino nitrogen and a fall in FFA level could be detected.