Previous studies showed that there is a marked difference among the dispersion characteristics of sendo samples, and the coating work with sendo seems to be highly lessened by their dispersiveness in water. Therefore, in this study the effects of bentonite and chemicals on dispersiveness of sendos in preparing mud suspension were studied by the authors. The results obtained are summarized as follows: 1)Two kinds of bentonite samples produced in Gunma and Shimane prefectures are used in this study. The former may be classified as alkali bentonite and the latter as alkaline-earth bentonite according to their chemical and physical characteristics. 2)Sendo samples contained 10 percent of Gunma bentonite were prepared with Akashi, Awaji, Hiroshima, Kyushu and Okayama Sendos, and dispersion characteristics of these samples were compared with that of a non-treated sample. It is found that pH value and dispersiveness are more or less increased by the addition of bentonite and its effect has been exhibited strongly upon sendos which coagulate markedly in water. And the effect of Shimane bentonite is much less than that of Gunma bentonite. 3)Kyu-Akashi sendo samples contained 0.5 percent of sodium carbonate or 0.25 percent of sodium silicate are also highly dispersive in water, while non-treated samples coagulate completely in water. A combination of bentonite with chemicals is superior to bentonite and chemicals used singly for the increase of dispersiveness of sendos.