The mutagenicity of the extracts from defatted rice bran by water or subcritical water treatment at 50°C to 250°C was examined using the Umulac AT test, which is a kit reagent for assaying the genotoxin-induced umu gene expression. The examination revealed that the extract at any temperature was negative for the mutagenicity for both the -S9 and +S9 tests, which assess the mutagenicity of the sample itself and its metabolites, respectively. © 2008, Japan Society for Food Engineering. All rights reserved.