An isolate of barley mild mosaic virus (BaMMV-Kor) obtained from Iri, Korea-was characterized and compared with three BaMMV strains, BaMMV-Nal and BaMMV-Kal from Japan and BaMMV-M from Germany. Mechanical inoculation experiments showed that BaMMV-Kor was similar to BaMMV-Nal, but differed from BaMMV-Kal and BaMMV-M, in its pathogenicity towards Japanese barley cultivars. However, BaMMV-Kor differed from BaMMV-Nal, as well as from BaMMV-Kal and BaMMV-M, in that it infected most of the Korean naked barley cultivars tested. BaMMV-Kor was distinguished from three other BaMMV strains by ELISA. The sequence of the 3'-terminal 2500 nucleotides [excluding the poly (A) tail] of RNA 1 of BaMMV-Kor was determined to start within a long open reading frame coding for a part of the NIb polymerase (468 amino acids) and the entire capsid protein (251 amino acids), which is followed by a non-coding region (NCR) of 342 nucleotides. The capsid protein of BaMMV-Kor shows higher amino acid sequence homology with BaMMV-Nal (97.2%) than with BaMMV-Kal (92.0%). Likewise, in the 3' NCRs, BaMMV-Kor shows higher nucleotide sequence homology with BaMMV-Nal (96.5%) than with BaMMV-Kal (92.1%). These results indicate that BaMMV-Kor is a new strain of BaMMV, which is closely related to BaMMV-Nal, but differs both biologically and serologically from the Japanese and German strains.