The objective was to evaluate the effect of pre-exposition of injectable progesterone to timed artificial insemination (TAI) protocol on conception rate of high production Bos taurus dairy cows. In the study, 293 Holstein and crossbred (Holstein X Jersey) dairy cows at 57,0±0,5 days in milk, body condition score of 2.72±0.01 (scale of 1 – 5) and production of 35,0±0,6 were used. Seven days before TAI protocol (D-7), cows were divided into two experimental groups (Control group and P4i group). In the Control group, cows received 2 mg of estradiol benzoate (RIC-BE, Agener, Brazil), 25µg de Lecirelina (Tec-relin, Agener, Brazil) and a progesterone intravaginal device (Primer, Agener, Brazil). After seven days (D7), cows received 500µg of Cloprostenol (Estron, Agener, Brazil). On day 8 (D8), the progesterone device was removed and cows received 500µg of Cloprostenol (Estron, Agener, Brazil) and 1 mg of estradiol cypionate (Cipiotec, Agener, Brazil). On the P4i group, cows received 300mg of injectable progesterone (Sincrogest Injetável®, Ouro Fino, Brazil) on D-7 and were submitted to the same synchronization protocol as the Control group. All cows were inseminated 48 hours after the removal of progesterone device. Ultrasound exams were performed 30 and 60 days after TAI to evaluate the conception rate at 30 and 60 days and pregnancy losses from 30 to 60 days after TAI. Statistical analyses were performed by GLIMMIX procedure of SAS and the binomial variables were presented by percentage. There was a statistical tendency in the conception rate at 30 days after TAI [Control 52.7% (77/146)B and P4i 61.2% (90/147)A; P= 0.10]. However, conception rate at 60 days after TAI [Control 50.9% (60/118) and P4i 58.5% (69/118); P= 0.23] and pregnancy losses [Control 4.7% (3/63) and P4i 2.8% (2/71); P= 0.45] were similar between groups. In conclusion, the pre-exposition to progesterone on TAI protocol tends to increase the conception rate at 30 days after TAI in high production Bos taurus dairy cows.