To examine whether fructose and xylitol increase the plasma concentration and urinary excretion of adenosine, as well as uridine and purine bases (hypoxanthine, xanthine, and uric acid), we intravenously administered xylitol and, 2 weeks later, fructose, to five healthy subjects. Analyses of blood and urine samples obtained during these infusion studies demonstrated that fructose increased the urinary excretion of adenosine and uridine 11.9- and 105.5-fold, respectively, and caused only a small increase in the plasma concentrations of uridine and purine bases. It was further demonstrated that xylitol increased the urinary excretion of uridine 58.4-fold, with a marked increase in the plasma concentrations of purine bases and uridine but without an increase in the urinary excretion of adenosine. However, neither infusion increased the plasma concentration of adenosine. These results suggest that in addition to many organs, including the liver, fructose is significantly metabolized by an abrupt adenosine triphosphate (ATP) consumption in the kidney, leading to an increase in the urinary excretion of adenosine and uridine. They also suggest that xylitol is not significantly metabolized in the kidney.