Metabolic effects of glucose, fructose, sorbitol, xylitol and their combinations during intravenous application in men were investigated. The totale and metabolic clearance, the renal and metabolic elimination, the half-time and the turnover rate were measured. For all sugars intravenous long-term infusions from six to twelve hours were performed. Up to a dosage of 0.75 g/kg/h for glucose 0.5 g/kg/h for sorbitol and 0.25 g/kg/h for fructose and xylitol a steady state of substrates and metabolites has been found. If these dosage-limits are exceeded during glucose application a hyperglucosemia, after sorbitol a continous rise in sorbitol blood level, during fructose a rise in lactate and during xylitol infusion clinical side effects occurred. It could be shown that during simultaneous application of glucose, fructose and xylitol the utilization of glucose rises whereas the utilization of fructose and xylitol remain on such levels as if these sugar were infused alone.