['To determine the impact of blastocyst transfer on an oocyte donation program.', 'Retrospective review of embryo transfer in an IVF clinic.', 'Private assisted reproductive technology unit.', 'Two hundred and twenty nine patients undergoing oocyte donation.', 'Culture of pronucleate embryos to either day 3 or day 5 followed by embryo transfer.', 'Implantation rates, pregnancy rates, and multiple gestations were analyzed.', 'Implantation rates and pregnancy rates were significantly increased by moving to extended embryo culture and transfer on day 5. After day 3 transfers, implantation and pregnancy rates were 47.1% and 75%, respectively. In contrast, on day 5 these rates were increased to 65.8% and 87.6%. Concomitantly, there were significantly fewer embryos transferred on day 5 (2.1) compared to day 3 (3.2).'] Does blastocyst culture and transfer increase the efficiency of oocyte donation?