In this study we want to emphasis the bactericidal, bacteriostatical and antifungal effect of isotiocyanates from horseradish roots on some microbial culture: Escherichia coli, Candida albicans, Bacillus subtilis, Staphylococcus aureus, Agrobacterium tumefaciens and Rhizopus nigricans. For this, at first were established the best conditions of working, namely: phosphate buffer pH was 7, reaction time was of 120 ÷ 330 minutes, temperature of 55°C, with a view to extracts obtained from cutting horseradish. Then, through inoculate dissemination technique on culture medium surface, were done microbiological tests. The obtained results, distinguished the bactericidal, bacteriostatical and antifungal effect of isothiocyanates on studied microorganisms.