The antibacterial activity of sulforaphane [4-(methylsulfinyl)butyl isothiocyanate] has been previously described. We have analysed the activities of 12 isothiocyanates (ITC) including sulphoraphane on 25 strains of Helicobacter pylori using an agar dilution assay. In addition, bactericidal effects against H. pylori were determined for the 6 most active ITCs, both directly and against intracellular bacteria in cultured human epithelial (HEp-2) cells. The MIC90 values for these ITCs ranged between 4 and 32 microg/mL and four of the most potent compounds exhibited bactericidal activity against both extra- and intracellular bacteria. Overall, our data indicate that ITCs have a potent antibacterial effect against H. pylori and these naturally occurring phytochemicals might have potential as novel therapeutic agents for H. pylori eradication.