In this paper the antimicrobial action of isothiocyanate, active principles from horseradish (Armoracia rusticana), on some bacteria: Escherichia coli, Candida albicans and Aspergillus niger were studied. In order to do that the extracts were obtained and then microbiological tests have been performed, using the technique of inocul dissemination on the media surface. It was remarked that the extracts from horseradish have antimicrobial effect on the studied bacteria.