Rice blast is one of the most serious diseases of cultivated rice. We characterize here the nucleotide variation present at nine blast resistance (R) genes within a collection of 13 indica and 13 japonica rice cultivars, along with 12 accessions of wild rice (Oryza rufipogon). Compared with other functional genes, high genetic diversity has been observed in blast R genes (mean nucleotide diversity of 3.2%), which might be the most important characteristics of blast R genes. Even if the overall diversity in R genes is high, the genes can also be divided into three types according to different degrees of conservation by principal component analysis: relative conservation (Pita, Pit, Pi5-1, and Pid-2), intermediate diversity (Pi37, Pib, and Pi9), and high diversity (Pi36 and Pikm-2), suggesting that these types of R genes might recognize different categories of molecules released by rice blast pathogens. Our data also revealed that a significant regression was observed between the wild and the cultivated accessions with respect to their u a , providing an indication that artificial selection has played an important role during the evolution of these R genes. High correlation between nucleotide diversity and K a /K s or R M in NBSencoding genes might be the clues for possible mechanisms of rapid evolution in these genes.