It has been reported that D-sorbitol enhances the absorption of vitamin B_<12> from the intestine (Greenberg, 1957,Chow, 1956,1958 et al.). The question of whether this effect of D-sorbitol is concerned only with vitamin B_<12> absorption or also with other kinds of vitamins is interesting and still controversial. For the purpose of clarifying this, clinical studies on the influence of D-sorbitol and various carbohydrates on the thiamine absorption were made. Human subjects were administered orally, in fasting state, in the early morning, 20 mg of thiamine with or without 5 g of D-sorbitol or carbohydrates. Amonunts of thiamine excreted in the urine during 24 hours following the administration were measured. The results obtained indicate that the absorption of thiamine can be enhanced not only by the addition of D-sorbitol, but also by that of D-glucose, D-fructose, inositol and DL-glucosamine, whereas D-mannitol and D-xylose do not have such an effect.