The Russian influenza A live virus vaccine (LIV) is based on the temperature sensitive (ts) and cold-adapted (ca) A/Leningrad/134/17/57 (H2N2) donor strain (Len/17). Reassortants between current circulating A strains and the ca donor strain are traditionally prepared in eggs. MDCK cells have been used for the commercial manufacture of inactivated whole virus influenza vaccines. There has, as yet, been no transition into cell culture for the development of LIV. In this report we have looked at cell-culture derived reassortants with respect to their ability to maintain their phenotypic and genetic characteristics.