Bacterial blight and fungal blast diseases ofrice, caused by Xanthomonas oryzae pv. oryzae andPyricularia grisea Sacc., respectively, are two of the mostdevastating diseases in rice worldwide. To study thedefense responses to infection with each of thesepathogens, expression profiling of 12 defense-responsivegenes was performed using near-isogenic rice lines thatare resistant or susceptible to bacterial blight and fungalblast, respectively, and rice cultivars that are resistant orsusceptible to both pathogens. All 12 genes showedconstitutive expression, but expression levels increasedin response to infection. Based on their expression patternsin 12 host-pathogen combinations, these genescould be classified into three types, pathogen non-specific(6), pathogen specific but race non-specific (4) andrace specific (2). Most of the 12 genes were only responsiveduring incompatible interactions. These resultssuggest that bacterial blight and fungal blast resistancesshare common pathway(s), but are also regulated bydifferent defense pathways in rice. Activation of thecorresponding R gene is the key step that initiates theaction of these genes in defense responses. The chromosomallocations and pathogen specificities of seven ofthe 12 genes were consistent with those of previouslyidentified quantitative trait loci for rice disease resistance,which indicates that some of the 12 genes studiedmay have a phenotypic impact on disease resistance inrice.