Background: In the last few years a significant resurgence of interest in the potential benefits of human oocyte cryopreservation has immerged. There is, however, little/no information regarding the fertilization and development potential of cryopreserved oocytes compared to fresh oocytes from the same women in the same cycle or comparison of freezing protocols. Objective: To compare oocyte survival, fertilization and cleavage rate between 2 different oocyte cryopreservation protocols in consenting patients undergoing IVF and ICSI. A comparison of the sibling fresh oocyte embryo development with the embryos derived from cryo will be compared at the completion of the study. Materials and Methods: Following standard controlled ovarian hyperstimualtion (Follistim AQ and Ganirelix Acetate, Organon Pharmacueticals USA, Inc.) for IVF, patients who had >10 MII oocytes, had 30% of their oocytes selected for immediate freezing and thawing using either the Boldt method (Sage Invitro Fertilization) or the Fabri method as published in the literature(HR'01). Oocytes were thawed after at least 15min in LN2 and surviving oocytes were injected by a standard ICSI technique 2-4hrs later, along with the remaining 70% of the patient's fresh, mature oocytes. Cryopreserved-thawed oocytes were cultured separately from untreated oocytes under oil in 5%CO2 in Sage cleavage medium. The best embryos, regardless of the treatment were considered for D3 transfer. Supernumerary embryos were cryopreserved on the day of ET or at Blastocyst stage. Results: The data represent the initial 19 patients, 10 in Fabri and 9 in Boldt. Oocyte survival and fertilization rates were similar between groups, 78.6% (44/56) and 70.5% (31/44), and 80.7% (46/57) and 69.6% (32/46) for Fabri and Boldt protocols, respectively. The percentage of embryos >6 cell were 7% (2/31) and 38% (12/32) for Fabri and Boldt, respectively (p<0.01). Conclusions: Although these data are preliminary and the study is still ongoing, both protocols appear to yield cryo-survival rates similar to those of 2PN's and fertilization rates by ICSI equal that achieved from the fresh oocytes. However the Boldt group had significantly better D3 embryo development. Future studies are planned to assess the implantation potential of the embryos derived from oocyte cryopreservation and whether the differences in D3 embryo development translate into differences in pregnancy.