Objective : To assess and compare the clinical outcomes between GnRH agonist long protocol and GnRH antagonist short protocol in oocyte donation program. Materials and Methods: Of total 18 oocyte donation cycles, controlled ovarian hyperstimulation (COH) were performed with GnRH agonist long protocol and GnRH antagonist short protocol in initial 9 cycles and later 9 cycles, respectively. Oral estradiol valerate and progesterone in oil we re administrated to all recipients for endometrial preparation. Oral estradiol administration was started from donor cycle day 1 after full shut down of gonadal axis with GnRH agonist in patients with ovarian function. Progesterone was injected from oocyte retrieval day of donor initially, then continuously till pregnancy 12 weeks if pregnancy was ongoing. We compared the parameters of clinical outcomes, such as number of the retrieved oocytes, fertilization rate, high grade embryo production rate, clinical pregnancy rate, implantation rate, ongoing pregnancy rate, COH duration, total gonadotropin dose for COH between GnRH agonist long protocol group and GnRH antagonist group. Statistical analysis was performed using Mann-Whitney test, p<0.05 was considered as statistically significant. Results: The number of retrieved oocytes, fertilization rate, high grade embryo production rate, clinical pregnancy rate, implantation rate, ongoing pregnancy rate were $14.89{\pm}7.83$, 81%, 64%, 78%, 31%, 78%, respectively in GnRHa long protocol group and $11.22{\pm}8.50$, 79%, 64%, 67%, 34%, 56%, respectively in GnRH antagonist group. There was no significant differences in parameters of clinical outcomes between 2 groups (all p value >0.05). Duration and total gonadotropin dose for COH were $10.94{\pm}1.70$ days and $43.78{\pm}6.8$ vials in 18 cycles, $12.00{\pm}1.73$ days and $48.00{\pm}6.93$ vials in agonist group, $9.88{\pm}0.78$ days and $39.55{\pm}3.13$ vials in antagonist group, respectively. In GnRH agonist long protocol group, significantly longer duration and higher gonadotropin dose for COH were needed (p=0.012). Conclusion: In oocyte donation program, clinical outcomes from controlled ovarian hyperstimulation with GnRH antagonist were comparable to those from GnRH agonist long protocol group, so controlled ovarian hyperstimulation with GnRH antagonist may be effective as GnRH agonist long protocol. At least there may not be harmful effects of GnRH antagonist on oocyte development and quality.