I performed the quantitative estimation of catalase in blood and tissues of acatalasemiacases, using Warburg's manometric method, that was applied according to Fujita-Kodama's technic, and following results were obtained: 1) When I performed the quantitative estimation of catalase in 1/1000 diluted blood as ordinary method, Qcat in blood of Acatalasemia were 0, but when I examined the quantity of catalase in the not diluted blood of acatalasemia, these Qcat were about 510. When I compared Qcat. of acatalasemia's blood with Qcat of a normal person's blood, the ratio between them was about 1/5001/1000 and then it was an extremely small amout. 2) The tissues of nose and mouth in acatalasemia cases contained no catalase