N-[beta-[4-(beta-Phenylethyl)phenyl]-beta-hydroxyethyl] imidazole hydrochloride (denzimol, Rec 15-1533), a new anticonvulsant drug, was tested using the Ames procedures with and without metabolic activation, on five strains of Salmonella tythimurium and using the host mediated assay with Schizosaccharomyces pombe as microorganism test. In both tests the drug did not show any mutagenic activity when compared with mutagenic standards.