Two virus strains, signed as A-Ck-VN-KH23-2013 and A-Dk-VN-KH24-2013 isolated in Khanh Hoa province, Vietnam in 2013, those virus strains were identified as clades 2.3.2.1 A and 2.3.2.1 C of the H5N1 avian influenza virus. Pedigree analysis based on nucleotide and amino acid sequence of the HA (H5) gene showed that the strain A-Ck-VN- KH23-2013, having close relationship with a number of the recently emerged strains of clade 2.3.2.1 in Vietnam (2011, 2012), China (2007, 2009, 2010), Mongolia (2009), Laos (2010) and the reference strain of A-Hubei-1-2010 (CY098758)/(clade 2.3.2.1 A), which was determined belonging to clade 2.3.2.1 A. Meanwhile, the strain A-Dk-VN-KH24-2013 arranging in the same group with the reference strain: A-HK-6841-201 0 (HQ626461 )/(clade 2.3.2.1 C) and some other strains of Vietnam (isolated in 2012) and a collection of the newly emerged strains in 2012 in Indonesia, which was determined belonging to clade 2.3.2.1 C. The A/H5N1 influenza virus, in Vietnam as well as in the other South-east Asian Nations, in recent time had developed further some sub-clades. To deal effectively with the bird flu, epidemic surveillance, application of preventive measures and use of vaccine with antigenic compatibility with those emerging clades, proceeding to generate the appropriate vaccines are essential requirements need to be undertaken in Vietnam.