Abstract: Genotoxicities of commercial hair dyes manufactured by two companies (SJ and CY) were determined by the micronucleus assay on the root-tip cells of Vicia faba. Dye solutions in the concentrations of 1.5, 4.5, 6.0, 9.0, 12.0 and 15.0 g/L were applied for the test. The presence of micronuclei was shown increased after immersing the cells in the hair dye solutions. It increased with increasing concentration initially and followed by a decline for both products. With SJ, the peak number of micronuclei was observed at the dye concentration of 9.0 g/L; and with CY, 6.0 g/L. Indicated by the rises of the micronucleus counts, there was apparently genomic damages to the plant cells caused by the hair dyes. It, therefore, implicated a safety concern on the products for consumers.