Background: Although the question about the mechanism of GnRH agonists and GnRH antagonists' action is well answered, there is still no clear answer about which analogue gives better results in clinical practice. The reports are contradictory and often favor one type of the analogue. Objective: To compare the impact of GnRH agonist and antagonist protocol during controlled ovarian stimulation cycles as regard the total number of oocytes retrieved and number of mature oocytes, fertilization rate, cleavage of embryos and their grading and pregnancy rate . Patients and methods: This prospective randomized controlled study was conducted at Al-Azhar University Hospitals; including 80 women undergoing controlled ovarian stimulation for ICSI. Patients were assigned randomly into two equal groups : group 1 received GnRH agonist long protocol, and group 2 received GnRH antagonist protocol. Patients underwent GnRH agonist long protocol were processed for pituitary down-regulation on luteal peak period with triptorelin injection for 14 days. A basic evaluation was conducted by ultrasound examination and blood test for hormone levels. After 5 consecutive days of fixed dose of r FSH (Gonal-F) medication, transvaginal ultrasound examination was performed to monitor the development of follicles, and the dose of rFSH was optimally adjusted based on the number and size of developing follicles. In the GnRH antagonist protocol, at day 3 of a menstrual cycle, a basic evaluation was conducted and rFSH (Gonal-F) was initiated at same day the GnRH antagonist, cetrorelix, was administered after 5 days of fixed dose of stimulation drug , and continued to the day of human chorionic gonadotropin (HCG) administration. Oocytes were retrieved 34-38 h after HCG injection and were fertilized in vitro. Embryo transfer (ET) was carried out 72 h after oocyte retrieval. Outcome measures were the total number of oocytes retrieved and number of mature oocytes, fertilization rate, cleavage of embryos and their grading and pregnancy rate. Results: There were no significant differences between two groups in the number of total oocytes retrieved, mature follicles, the number of embryos transferred, treatment duration and gonadotrophin consumption. Both groups showed similarities in the rate of chemical and clinical pregnancies. The rate of chemical pregnancy was higher (46.9%) in the GnRH antagonist protocol compared with long GnRH agonist group (40.6%). However, this rate did not reach a statistically significant level. The  rate of clinical pregnancy was (31.3%) in antagonist group versus (28.1%) in agonist group. Conclusion: On the basis of these results, we offered  using GnRH antagonist  as a patient friendly protocol in ART with immediate mode of action, similar pregnancy rate, time saving, more flexibility of treatment ,and it may be easier or more convenient to administer.