The suitability of maltose for parenteral nutrition was investigated in metabolically healthy volunteers. A solution containing 20% of maltose was infused intravenously for four hours using three different doses (0.125 g/kg; 0.25 g/kg; 0.5 g/kg BW/h). Following cessation of the infusions the laboratory controls were carried on for four more hours. The infusions of maltose were tolerated without any complications. However, only when using the lowest dosage a steady state in blood concentration of maltose was reached, i.e. in the case of 0.125 g/kg BW/h. The results show that in humans the metabolic capacity for maltose is limited. The glucose concentration in blood remained almost unaltered during maltose infusion, while the serum insulin concentration was slightly elevated. A further sign for metabolism of maltose was the decrease in free fatty acid concentration. Because of the low metabolic capacity for maltose the urinary loss (in the form of maltose and glucose) is high with greater infusion rates and amounts to 20-30% of the intravenous load. A greater part of the sugar excreted in the urine consists of glucose, despite an almost normal blood glucose concentration. Considering the results of the experiments with volunteers it is concluded that maltose is not suited for intravenous therapy. Because of the low metabolic capacity of the human organism the renal losses are too great.