The current study was conducted on a total of 204 Egyptian, lactating buffalo cows. These animals were in the second or third parity, of good body condition scores and apparently healthy. The animals were raised in intensive production system on a private farm. The buffalo cows were allotted into three groups, two of these groups were experimental and the third was a control group. The first experimental group included 30 buffalo cows were undergo ovulation control by Crestar® a subcutaneous ear implant ( 3mg norgestamet ) plus Crestar® injection i.m. ( 3mg norgestamet + 5mg estradiol valerate ) at zero day. At the 7th day of implantation, PGF2α was injected i.m., then Crestar® implant was removed at the 9th day with injection of PMSG 400 iu. Timed insemination was conducted 56 hrs later. The second experimental group (24 buffalo cows) was treated by the same program, moreover they injected with GnRH at the time of insemination .The third group (150) buffalo cows was bred naturally and used as a control group. For serum progesterone assay blood samples were collected from the animals of the two experimental groups at day 0, 7 and 9 of the Crestar program. The buffalo cows of the experimental groups were closely observed for estrus signs and were rectally palpated at the time of insemination for detection of the internal estrus changes. At day 50 post insemination all animals were rectally palpated for pregnancy diagnosis. The result of the current study revealed that the visibility of estrus signs were 20 %, 16.7% and 22 % for the first, second and third group respectively. Pregnancy rate was much higher in the second group associated with the injection of GnRH at the time of insemination. Two animals of the second group were carrying twins (11 %). Serum level of progesterone was significantly higher in the 7thday in comparison with those recorded for 0 and 9th day.