This article presents the results of studies on determination of optimal parameters of recombinant strains A/NYMC X-217 (H3N2) and B/NYMC BX-49 of influenza virus cultivation in chicken embryos. It is found that a maximum virus accumulation is formed under the following cultivation conditions: age of chicken embryos is 9-11 days in case of inoculation of the allantoic cavity, inoculated virus dose - 1,000-10,000 EID50, temperature and time of incubation - (34 +/- 0.5) degrees C and 48 h, respectively. If the cultivation parameters are satisfied, it is possible to obtain a highly active viruscontaining material with infectious and hemagglutinating activity, as well as a content of hemagglutinin not less than 7.0lg EID50/ml, 1: 256 and 7.0 mu g/ml, respectively, that is enough to prepare a trivalent inactive seasonal influenza split vaccine.