Cymiazole hydrochloride is the active component of the acaricides Apitolc and Apichemc, which are used as varroacides in beekeeping. Considering that residues of cymiazole hydrochloride were detected in all bee products being used for human nutrition and as alternative medications in human and veterinary medicine, the aim of this study was to evaluate the ability of this substance to produce genotoxic effects in human peripheral blood lymphocytes. The genotoxic effects were studied by sister chromatid exchange (SCE) test in vitro. The results obtained for all doses applied to the cultures (0.01; 0.10 and 1 mg/ml) showed very significant increases in frequencies (p<0.001) of SCEs in comparison to the negative control, i.e. cymiazole hydrochloride exhibited genotoxic properties.