Nine combinations of dosages and concentrations of D‐xylose were given orally to eight clinically normal, immature dogs. The concentrations and dosages of D‐xylose consisted of 5%, 10%, and 20% at 250 mg/kg, 500 mg/kg, and 750 mg/kg. Serum samples were collected at 0, 30, 60, 90, 120, and 180 minutes. Serum xylose was quantitated using the phloroglucinol microassay technique. A peak in serum xylose concentration was seen for each treatment combination at 60 or 90 minutes after dosing. The dosage effect was important in influencing serum xylose values (P<0.0001). As the test solution dosages increased from 250 mg/kg to 500 mg/kg and 750 mg/kg, serum xylose values (when dosage was analyzed over the length of the entire test) rose linearly (R2= 0.98). The treatment combinations of 5% and 20% xylose solutions dosed at 750 mg/kg produced the highest serum xylose values at the 60‐and 90‐minute peak intervals. The independent effect of concentration was significant (p0.05) when the 5%, 10%, and 20% solutions were compared at a specific