Findings from the comparative study of the immunobiological properties of live brucellosis vaccines in guinea pigs are presented in the article. Vaccines from strains Brucella abortus 19 (U.S.) and 82 (Russia), in the S and SR forms, respectively, exhibited the highest and most pronounced immunological efficacy, whilevaccinesfromstrainsB.abortus82-PS(intheRSform)andB.abortusRB-51and75/79-AB(intheR forms)exhibitedthelowest.ThelivevaccinefromstrainB.abortus82,togetherwithahighimmunological activity,possessesinagglutinogenicproperties.Thegreatadvantageofthisvaccineoverthevaccinefrom strain B. abortus 19 is that after its use in animals the problem of the differential diagnosis of brucellosis becomes much simpler. The live vaccine from strain B. abortus 82 was adopted in veterinary practice in the Russian Federation; it is widely used for the targeted prevention of bovine brucellosis, but can also be used successfully for wild animals such as bison, deer, elk, and others.