The results of investigatiolls on the effect of soil microflora on Rhizobium and Bradyrhizobium strains development, their symbiosis activity with Legume plants and the effect of joined seeds inoculation with specific symbiotic bacteria and Azospirillum or/and Azotobacter strains are discussed. The results show the presellce of high number of antagonistic microorganisms to symbiotic bacteria, which could inhibit their growth, proliferation and survival in soil environment. This confirms the necessity of pre-sowing Legume plant seeds inoculation with specific symbiotic bacterial strains. Many investigators have observed the beneficial effect of joined Legume plant seeds inoculation with specific symbiotic bacteria and correctly selected Azotobacter or/and Azospirillum strains on symbiosis effectivity. The studies have shown that the effect of joined inoculation is influenced by plant species and cultivars, strain properties, the ratio of inoculant cell number in prepared inoculum, and the way and term of inoculum application. The studies leading to the explanation of mechanisms of the Azospirillum and Azotobacter influence on symbiosis are also discussed here.