Epoxide hydrolase hydrates epoxides to vicinal diols in the phyto-oxylipin peroxygenase pathway resulting in the production of epoxy alcohols, dihydrodiols, triols and epoxides, including many lipid epoxides associated with resistance. Two epoxide hydrolase genes from Nicotiana benthamiana L., NbEH1.1 and NbEH1.2, were amplified from coding DNA of leaves during a susceptible response to the hemibiotrophic pathogens, Colletotrichum destructivum O'Gara, Colletotrichum orbiculare Berk. and Mont. von Arx. or Pseudomonas syringae pv. tabaci Wolf and Foster, or the hypersensitive resistance response to P. syringae pv. tabaci expressing avrPto. Increases in expression of NbEH1.1 generally occurred during the late biotrophic and necrotrophic stages in the susceptible responses and before the hypersensitive response. NbEH1.2 expression was not significantly induced by C. orbiculare but was induced by C. destructivum, P. syringae pv. tabaci and P. syringae pv. tabaci expressing avrPto, although to a lesser degree than NbEH1.1. Virus-induced gene silencing of NbEH1.1 delayed the appearance of lesions for C. destructivum, reduced populations of P. syringae pv. tabaci and increased populations of P. syringae pv. tabaci expressing avrPto. The importance of epoxide hydrolase during pathogen attack may be related to its roles in detoxification, signalling, or metabolism of antimicrobial compounds.