Objective: We evaluated the efficacy of blastocyst transfer in decreasing the incidence of high-order multiple gestations after in vitro fertilization. Study Design: We conducted a retrospective analysis of 218 patients who were undergoing in vitro fertilization and by our criteria of three 8-cell embryos on day 3 could receive either a day 3 transfer of cleaved embryos or a day 5 transfer of blastocysts. Ongoing pregnancy rates, implantation rates (determined by the total number of visualized gestational sacs), and multiple pregnancy rates were compared between the 2 groups. Results: Respective day 3 and day 5 ongoing pregnancy rates (61% and 51%) and implantation rates (35% and 33%) were not significantly different. There were 9 triplet or higher gestations in the day 3 group and 0 in the day 5 group. Conclusion: Blastocyst transfer can be used to reduce the number of embryos transferred and the resultant incidence of high-order multiple pregnancies while maintaining high pregnancy rates. (Am J Obstet Gynecol 2000;183:377-82.)