The review characterizes the currently used cold-adapted donor strains of influenza virus attenuation to prepare cold-adapted reassortants with actual epidemic influenza virus strains. It considers new procedures for preparing attenuated influenza virus strains for live influenza vaccines, as well as analytical methods and the genome composition of reassortants. Recent data on the safety of live cold-adapted influenza vaccines (LCAIVs), including those on the genetic stability of vaccine reassortants and the immunogenicity and efficacy of these vaccines for different age groups, are discussed. There is evidence for the design of live human vaccines against avian influenza. It is concluded that LCAIVs are highly effective for immunization of children.