Live attenuated cold-adapted influenza vaccine (LIV) has been used In Russia for over 50 years and proved to be safe and effective. Currently, Russian reassortant LAIV is based on Influenza A/Leningrad/134/17/57 (H2N2) and B/USSR/60/69 Master Donor Viruses (MDVs) which are cold-adapted (ca), temperature-sensitive (ts), and attenuated (art), respectively. The MDVs are used to generate attenuated reassortant vaccine viruses containing the surface antigens of current wild type (wt) influenza A (H1N1) and A (H3N2) viruses and wt influenza B virus. The cal tslatt phenotype of these viruses limits replication In the upper respiratory tract. Reassortment typically yields numerous viruses with different genome constellations, rapid screening is needed to select proper vaccine viruses. In this study, screening of reassortant vaccine strains for live attenuated influenza vaccine generated from currently circulating influenza A and B viruses by RFLP assay is described.