Mutagenicity of white layer cake including 20 kGy-gamma irradiated egg white manufactured as a research on the practical approaches of gamma irradiation for the reduction of egg allergy was evaluated by Salmonella typhimurium reversion assay (Ames test). The water-soluble and organic solvents mixture of methanol: chloroform (2 : 1)-soluble fractions of the white layer cake including 20 kGy-gamma irradiated egg white were examined in S. typhimurium TA98 and TA100. Both with and without metabolic activation, the number of revertant colonies were not increased in each extract compared with negative controls. No significant difference in the formation of the colonies was observed at the non-irradiated and 20 kGy-irradiated samples. The results indicate that there is no evidence of mutagenicity in white layer cake including 20 kGy-gamma irradiated egg white.