['To determine the feasibility and success of blastocyst-stage embryo transfers in patients having only fair and poor quality cleavage-stage embryos on day 3.', 'Prospective case study with historic controls.', 'Tertiary care private hospital IVF center.', 'A total of 158 day 5 embryo transfer cycles in patients with grade 3 and grade 4 cleavage-stage embryos. Control group consisted of 162 day 3 transfer cycles performed with embryos of similar quality.', 'In vitro culture of embryos up to the blastocyst stage.', 'The percentage of cycles that culminated in the transfer of at least one blastocyst and implantation and pregnancy rate related to the day of transfer.', 'In the day 3 transfer group, a mean of 5.2 embryos were replaced per patient. This was significantly more than the mean of 2.4 embryos that could be replaced on day 5 (P <.001). The clinical pregnancy rate per embryo transfer was 27.2% and 33.5% in the two groups, respectively (P >.05). The implantation rate per embryo was significantly higher in the day 5 transfer group (15% vs. 5.9%). The multiple pregnancy and abortion rates were similar between the groups.'] Does blastocyst-stage transfer of poor-quality cleavage-stage embryos result in higher implantation rates?