According to 'the Regulation of Reporting of Notifiable Animal Diseases in Turkey', the valid diagnosis for Brucellosis in livestock, which is in the list of notifiable animal diseases, is the isolation and identification of Brucellae as the gold standard as mentioned in 'the Regulation of the Fight with Brucella'. In the context of 'The Brucellosis Control and Eradication Program' in Turkey, where mass vaccination is practised as a part of this program in livestock, serological diagnosis is not considered to be valid except for Brucella free herds. While most of the current molecular techniques can differentiate Brucella organism at the genus level, they generally cannot make differentiation at the biovar-level. The primary purpose of this study is to determine the most prevalent Brucella biovars and the biovar distribution of Brucella isolates from the abort cases of livestock between 2010 and 2015 in Turkey. In this study, 5203 Brucella field isolates sent to our laboratory from different parts of Turkey for Brucella species and biovar identification between 2010 and 2015 were biotyped through conventional biotyping procedures. According to the results showing the percentages of dominant biovars causing brucellosis in livestock, the most common biovar was B. abortus biovar-3 in cattle and B.melitensis biovar-3 in sheep and goats. Vaccine strains isolated from goats were not included in biovar distribution in this study.