Hydrogen peroxide (H 2 O 2 ) is usually generated by normal aerobic respiration of pathogens and by the host defense response during plant–pathogen interactions. In this study, histochemical localization of H 2 O 2 accumulation in rice inoculated with the wild-type strain (PXO99 A ) and the gene deletion mutant (ΔahpC) of alkyl hydroperoxide reductase subunit C (AhpC) of Xanthomonas oryzae pv. oryzae (Xoo), the bacterial blight pathogen of rice, was analyzed. The ΔahpC mutant displayed a significant decrease in endogenous H 2 O 2 accumulation which was induced by the compensatory increase in H 2 O 2 scavenging activity. The change in the bacterial endogenous H 2 O 2 level affected the total amount of H 2 O 2 accumulation during the interaction with rice plants. These results suggested that Xoo contributes to H 2 O 2 accumulation in rice in a compatible interaction, and pathogen-driving H 2 O 2 is in association with cell collapse of rice.