The way of preserving blood specimens is an important factor on the screening tests for acatalasemic gene carrier. Because, the decay time of catalase activity in blood depends on the physical conditions, largely on temperature, where the blood specimens are kept. The author investigated the decay rate of catalase activity under following conditions. 1. Preservation of human blood in a vacuum flask at the temperature of 0～10℃. 2. Preservation in a deep-freezer at -20℃. In the former condition the blood specimen did not lose catalase activity at least seven days, and afterwards decay went on gradually. On the contrary, in the latter frozen specimens some degree of decay occurred soon. Afterwards, however, they kept constant catalase activity, 84% of the initial value, for months. So, it is concluded that for the practice of screening tests preservation in a vacuum flask at the temperature of 0～10℃ is preferable. Next, the author devised a handy, feasible way of screening tests named the !! floating disk method. !! It is a modification from M. Gagnon's estimation of catalase activity by measuring floating time of a piece of paper disk dipped with enzymatic specimen in hydrogen per-oxide solution. The screening level set up by this method is 12.5cm for the depth and 13.5 sec for the floating time.