The reassortants obtained via the crossing of highly productive influenza virus A/Puerto Rico/8/34 (H1N1) strain and the low pathogenic avian influenza virus A/Duck/Primorie/2621/2001 (H5N2) strain were genotyped and characterized. The H5N2 reassortant having 6 genes from A/Puerto Rico/8/34 virus has the high level of reproduction in chick embryos, while slightly more moderate than in the parent A/Puerto Rico/8/34 strain. The reproduction of the H5N1 reassortant that had 7 genes from A/Puerto Rico/8134 virus was very low. The serial passage selection allowed the investigators to obtain the H5N1 strain that was reproductively close to the H5N2 reassortant. This variant had one amino acid substitution in hemagglutinin (N244D, H3 numbering) and a lower affinity for fetuin. By the level of virulence to mice, the H5N1 and H5N2 reassortants were close to A/Puerto Rico/8/34 virus and greatly differed in this respect from low virulent A/Duck/Primorie/2621/2001 (H5N2). The results are discussed in connection with the problem of vaccination when there is a threat for H5N1 virus subtype-caused pandemic.