Meatballs were prepared by mixing ground beef and spices and inoculated with E. coli O157:H7, L. monocytogenes, and S. enteritidis before packaged in modified atmosphere (3% O(2) + 50% CO(2) + 47% N(2)) or aerobic conditions. The packaged samples were irradiated at 0.75, 1.5, and 3 kGy doses and stored at 4 degrees C for 21 d. Survival of the pathogens, total plate count, lipid oxidation, color change, and sensory quality were analyzed during storage. Irradiation at 3 kGy inactivated all the inoculated (approximately 10(6) CFU/g) S. enteritidis and L. monocytogenes cells in the samples. The inoculated (approximately 10(6) CFU/g) E. coli O157: H7 cells were totally inactivated by 1.5 kGy irradiation. D(10)-values for E. coli O157: H7, S. enteritidis, and L. monocytogenes were 0.24, 0.43, and 0.41 kGy in MAP and 0.22, 0.39, and 0.39 kGy in aerobic packages, respectively. Irradiation at 1.5 and 3 kGy resulted in 0.13 and 0.36 mg MDA/kg increase in 2-thiobarbituric acid-reactive substances (TBARS) reaching 1.02 and 1.49 MDA/kg, respectively, on day 1. Irradiation also caused significant loss of color and sensory quality in aerobic packages. However, MAP effectively inhibited the irradiation-induced quality degradations during 21-d storage. Thus, combining irradiation (3 kGy) and MAP (3% O(2) + 50% CO(2) + 47% N(2)) controlled the safety risk due to the potential pathogens and maintained qualities of meatballs during 21-d refrigerated storage.