Methods Loading tests were performed after the following preparation:(a) supper on the previous evening did not include fruits, vegetables or sugar;(b) patient fasted for 14 hours;(c) the control urine specimen before the test was sugar-free. The dose of fructose administered was I g. per kg. body weight unless otherwise stated. Total blood sugar was estimated by the method of Rappaport and Eichhorn (1950), blood fructose by the method of Patterson and Herbert as modified by Thompson and others (Behrendt, 1949). Blood dextrose was calculated by subtracting blood fructose from total blood sugar. Urine was collected hourly by indwelling catheter. As the sugar in the urine had been shown to be fructose only, urinary fru: tose was determined by the method of Fehling, but each specimen was also checked with glucose oxidase paper (Clinistix-Ames). Several urine specimens were examined also by paper chromatography (butanol acetic acid). Serum inorganic phosphorus was measured by the method of Fiske and Subbarow (1925).

Results Fig. 2 shows the curve of blood fructose concen-tration in the patient after an oral and intravenous load, as compared to the blood fructose curve in a normal child of the same age after an oral fructose load. It is seen that the blood fructose level in the control subject after the oral fructose load, increases slightly and returns gradually to the fasting level after four hours. In the patient the same oral dose