Genotoxic and mutagenic effects of aqueous extract from aerial parts Linaria genistifolia (L.) Mill. subsp. genistifolia, Plantaginaceae (Lg-ext) were investigated by using both Allium cepa root meristematic cells and bacterial reverse mutation assay in Salmonella typhimurium TA98 and TA100 with or without metabolic activation system (S9), respectively. In Allium root growth inhibition test, EC50 value was determined approximately 15 g/L and 0.5xEC50, EC50 and 2xEC50 concentrations of Lg-ext were introduced to onion tuber roots and distilled water and methyl methane sulfonate (MMS, 10 ppm) used as a negative and positive control, respectively. The characteristic effect caused by tested preparations was an increase of mitotic index (MI) in 7.5 g/L and 15 g/L (except 24 and 96 h) and simultaneous decrease of MI in 30 g/L and in MMS. While stickiness, bridges, chromosome laggards and disturbed anaphase-telophase were observed in anaphase-telophase cells, c-metaphase, pro-metaphase, polyploidy and binuclear cells were observed in other cells. Lg-ext was not found to be mutagenic on S. typhimurium TA 98 and TA100 with or without S9. The results were also analyzed statistically by using SPSS for Windows, and Duncan's multiple range tests were performed respectively. These results indicate that Lg-ext exhibits genotoxic activity in A. cepa root meristematic cells but not mutagenic activity in Ames test system