In order to obtain the ground for dose setting in radiation sterilization of dializers, radiation resistances of 185 non-sporeformer strains and 52 sporeformer strains, which were washed out of 43 products sampled from 10 lots, were examined comparing with the radiation resistance of Bacillus pumilus ATCC 27142 spore. Radiation resistances of the non-sporeformer strains were examined in the form of the suspension in phosphate buffer solution, and all the strains were confirmed to have lower resistance than B.pumilus spore. On the other hand, radiation resistances of the sporeformer strains were examined in the form of the cellulose fiber strip, on which water suspension of the purified spored was dropped and then air-dried. It was found that 11 strains of the 52 strains showed higher resistance than B.pumilus spore. The strongest strain was identified to be B.megaterium and found to have about 40 percent higher D-value then B.pumilus spore. As the result of the present study it was decided to use both B.pumilus ATCC 27142 and the B.megaterium as biological indicators, with which dializers are to be loaded for the dose setting experiment.