Effects of the thermal waters of Misasa (radioactive spring, Rn-content 180-360 mmC per liter), Hamamura (radioactive, calcium sulfate containing muriated spring), Tottori (sulfated muriated spring), and Yanahara (acid vitriol copper spring) were investigated. Two hundred milliliters of the thermal waters, (as Yanahara Hot Spring is too strongly acid, pH 0.5, Yanahara water was diluted 20 times with common plain water, and 200 mls of this diluted water was used) were administered to 32 consecutive patients with duodenal tube. And their effect on bile excretion was compared with that of 33% Magnesium sulfate solution. By the intraduodenal application of Yanahara water the amount and pigment concentiaton of the excreted bile were significantly increased than by the control. After the use of Hamamura it was shown that the amount of bile decreased while the pigment concentration increased than after the use of control. Effect of Misasa and Tottori waters was, concerning both amount and concentration of bile, less marked than the Magnesium sulfate solution. Sulfate ion content was 48g/ℓ in Yanahara, 0.29g/kg in Hamamura, 1.75g/kg in Tottori, 0.18g/ℓ in Misasa, and 288g/ℓ in Magnesium sulfate solution. Therefore no definite correlation was observed between the effect of these thermal waters aud their sulfate ion content.