Objective: To evaluate the graduated embryo score (GES) for predicting assisted reproductive technology (ART) outcome compared to a single morphologic evaluation on day 3 of culture (grade A: greater than or equal to 7 cells; <20% fragmentation). Design: Prospective cohort analysis. Setting: Private practice. Patient(s): Women aged <40 years with a normal uterine cavity treated with ART (n = 106). Intervention(s): Embryos were graded by GES and by day 3 morphologic characteristics alone before ET. Cycle outcomes were compared with embryo grade. Main Outcome Measure(s): Ongoing gestation and implantation rates. Result(s): Overall ongoing gestation and implantation rates were 48% and 26%, respectively. With 1 + embryo GES greater than or equal to70 (n = 77), the rates were 62% and 36%, respectively, which were significantly higher than for those with 0 embryos GES greater than or equal to70 (n = 29). With 1+ grade A embryo (n = 102), the rates were 50% and 27%, respectively. Transfer of more than one embryo GES greater than or equal to70 did not improve the pregnancy rate, but did increase the risk of multiple gestations. A single day 3 evaluation had an extremely low specificity (7%) compared to GES (47%). Graduated embryo scoring (GES) was an excellent predictor of pregnancy and implantation rates from blastocyst transfer. Day of transfer did not affect pregnancy rates, although implantation was higher from day 5 embryo transfer (ET) than from day 3 ET, as fewer embryos were transferred. Conclusion(s): Transfer of one or more embryo GES greater than or equal to70 predicts pregnancy and implantation rates better than a single morphologic evaluation on day 3 and achieves ART outcomes associated with blastocyst transfer from day 3 ET, making extended culture unnecessary for most patients. (C) 2003 by American Society for Reproductive Medicine.