Objective:To determine the relationship between blastocyst quality and the results of embryo transfer at the blastocyst stage.Design:Retrospective case analysis.Setting:Tertiary care private hospital IVF center.Patient(s):A total of 350 blastocyst-stage embryo transfer cycles.Intervention(s):In vitro culture to the blastocyst stage was undertaken in 350 ICSI cycles where four or more cleavage-stage embryos were available on day 3.Main Outcome Measure(s):Relationship between blastocyst quality and implantation and clinical and multiple pregnancy rates.Result(s):Transfer of at least one grade 1 or grade 2 blastocyst or one hatching blastocyst was associated with very high implantation and pregnancy rates. However, transfer of grade 3 blastocysts yielded very low implantation and pregnancy rates.Conclusion(s):There appears to be a strong correlation between blastocyst quality and success of blastocyst transfer.