¹Department of Reproduction and Artificial Insemination, Faculty of Veterinary Medicine, University of Kafkas, TR36100 Kars - TURKEY DOI : 10.9775/kvfd.2018.21505 Repeat breeder (RB) is one of the crucial causes of economic loss in dairy cows. The aim of this study was to determine the effects of intrauterine carvacrol administration after timed artificial insemination (TAI) on the conception rate (CR) in RB cows. The study involved 155 RB cows returned to service for more than three times and without any significant pathologic defects in genital tract. All cows were subjected to following estrus synchronization method: An intra-vaginal apparatus (IVA) containing 1.55 g progesteron were inserted for 9 days and administered one dose of PGF2α one day before removing IVA, then injected one dose of GnRH 6 hours before TAI. All the cows were inseminated in 56th hours after removing IVA. All RB cows were randomly divided to three groups. Group I (GI; n=52) and group II (GII; n=51), treatments groups were infused with 0.1% diluted Carvacrol and 0.1% Lugol"s (GII) solution. Group III (GIII; n=51) the control group, was received normal saline only. All infusions were administered one dose of 30-50 ml (according to uterine size) into uterus half hour after insemination. In the observations performed in 21 to 30 days after insemination, non-return rates (NRR) were 71.15%, 69.23% and 68.62% in groups of GI, GII and GIII, respectively. CR detected by rectal palpation at 60 days following artificial insemination were 67.30%, 63.46% and 46.15% in GI, GII and GIII, respectively. However, the differences between groups were not statistically significant. As a result: In the treatment of RB cows, it may be suggested that carvacrol infusion to the uterus may be preferred as it has improved pregnancy rates to some extent. Nevertheless, further investigations are needed to confirm these results. Keywords : Cow, Carvacrol, Artificial insemination, Repeat Breeder, Estrus synchronisation, Progestron, PRID, PGF2α, GnRH