As the amount of thiamine absorbed from intestinal tracts is only limited one and much of thiamine is excreted into feces, we tried to find out active agents to promote intestinal absorption of thiamine with their simultaneous oral administration by measuring the increase of urinary thiamine excretion. Ten mg of sodium oleyl methyl taurate (OMT) orally given to rats with 5 mg of thiamine stimulated their urinary thiamine excretion ; 0.85 mg of thiamine were found in 24-hour urine while 0.20 mg of thiamine in case of thiamine alone administrated. 30 mg of OMT with 5 mg of thiamine showed about sevenfold increase of the urinary thiamine in 24 hours (e. g. 1.43 mg). Thiamine in feces was decreased as the amount of OMT given was increased. No effect was observed with Tween 60,Span 20,CMC, sodium alginate, powdered bile, lecithin, Aerosol OT, sodium cholate or sodium taurocholate.