The influence of sonre factors involved in radappertization of meats on the radiation resi::tance of two isolates of Moraxella-Acinetobacter (M-A), Micrococc:us radiodurans, Escherichia coli, and Bacillus cereus spores was de :ermined. Combinaton of subfreezing temperature and lyophilizatian increased the resistance of vegetative cells and showed M-A isolates to be most resistant. Cells lyophilized in ground beef were le! s resistant than cells lyophilized in a commercial culture medium. A preirradiation heat treatment prior to lyophilization sensitized the cells to radiation. No appreciable difference in resistance was found with the presence of up to 8% sodium chloride during irradiation of M-A and M. radiodurans. The radiation resistance of B. cereus spores was not affected by changes in temperature, drying, or suspending medium to the same extent as were the vegetative cells. B. cereus spores were more resistant at ambient temperature than at.--30 +_ 10°C. AU these factors must be considered in assc:ssing the magnitude of radiation resistance of various organisms, br cause there is no predictable pattern of radiation resistance.