Abstract: This study was carried out to compare the pregnancy rates in timed artificial inseminations after Ovsynch and PGF2α + GnRH applications on lactating dairy cows. The research was conducted in a commercial dairy farm on 84 lactating Holstein cows which the ages were ranging between 3-5 years old and between 80-120 days postpartum. The cows were randomly assigned to two groups as Ovsynch (n = 42) and Prosta Glandin (PG) (n = 42). The cows in Ovsynch group recieved 10.5 μg-1 GnRH at day 0, 500 μg-1 PGF2α at day 7 and 10.5 μg-1 GnRH at day 9 intramuscularly. The cows in PG group recieved 500 μg-1 PGF2α two times with an interval of 14 days and 10.5 μg-1 GnRH intramuscularly 48 h after the second PGF2α injection. Artificial inseminations were applied to the cows in both of the groups between 16-20 h after the GnRH injections. The pregnancy diagnosis was performed 30 days after the artificial inseminations by ultrasonography. The pregnancy rates were determined as 35.7% (15/42) in Ovsynch group and 47.6% (20/42) in PG group. Although, the pregnancy rate were higher in PG group than the Ovsynch group the differrence was not statistically important (p>0.05). It was concluded that the programme consisted of 14 days interval double dose PGF2α injections, GnRH applications 48 h following the second PGF2α injection and timed artificial insemination 16-20 h after the GnRH injection could be an alternative to the Ovsynch programme in timed artificial inseminations.