Irradiation of ground beef and beef liver inoculated with Campylobacter jejuni was performed with gamma rays from a cobalt 60 source. Samples were packaged in gas barrier bags, sealed in air or under vacuum, and irradiated under refrigerated or frozen conditions. D10 values (dose required to inactivate 90% of a microbial population) ranged from 0.21 to 0.46 kGy in ground beef and from 0.26 to 0.69 kGy in beef liver. The D10 value for beef liver was higher than for ground beef under each irradiation condition, with the highest values being obtained under vacuum and frozen conditions.