Objective:To evaluate the accuracy of a scoring system combining zygote and embryo morphology in predicting the outcome of in vitro fertilization (IVF) treatment. Methods: In a study group, 117 consecutive IVF or intracytoplasmic sperm injection (ICSI) cycles with embryo transfer were carried out and 312 embryos were scored using a combined scoring system (CSS) of zygote and embryo morphology before transplantation. In a control group, a total of 420 IVF or ICSI cycles were carried out and 1176 embryos were scored using a cumulative embryo score (CES). The effects of the combined scoring system on the embryo implantation rate and pregnancy rate per cycle were analyzed. Results: Using the combined scoring system, the embryo implan-tation rate (27.6%) and the clinical pregnancy rate (48.7%) were significantly higher than those in the control group (20.8% and 38.6%, respectively). Also, the implantation rate of embryos scoring ≥70 (38.5%: 82 sacs/213 embryos) was significantly higher (P<0.001) than that of embryos scoring <70 (4%: 4 sacs/99 embryos). The pregnancy rate of patients with embryos scoring ≥70 using the combined scoring system (66.7%) was significantly higher (P<0.001) than that of patients with embryos scoring ≥20 using the cumulative embryo score (59.0%). Conclusion: The results suggest that selecting embryos with a high score (≥70) using the combined scoring system could increase the implantation rate and pregnancy rate, and that using a scoring system combining assessments of human zygotes and pre-implantation embryos might predict IVF outcomes more accurately than using a cumula-tive embryo score. Objective: To evaluate the accuracy of a scoring system combining zygote and embryo morphology in predicting the outcome of in vitro fertilization (IVF) treatment. Methods: In a study group, 117 consecutive IVF or intracytoplasmic sperm injection (ICSI) cycles with embryo transfer were carried out and 312 embryos were scored using a combined scoring system (CSS) of zygote and embryo morphology before transplantation. In a control group, a total of 420 IVF or ICSI cycles were carried out and 1176 embryos were scored using a cumulative embryo score ( Results: Using the combined scoring system, the embryo implan-tation rate (27.6%) and the clinical pregnancy rate (48.7%) were significantly higher than those in the control group (20.8% and 38.6%, respectively). Also, the implantation rate of embryos scoring ≥70 (38.5%: 82 sacs / 213 embryos) was significantly higher <0.001) than that of embryos scoring <70 (4%: 4 sacs / 99 embryos). The pregnancy rate of patients with embryos scoring ≥ 70 using the combined scoring system (66.7%) was significantly higher of patients with embryos scoring ≥20 using the cumulative embryo score (59.0%). Conclusion: The results suggest that selecting embryos with a high score (≥70) using the combined scoring system could increase the implantation rate and pregnancy rate, and that using a scoring system combining assessments of human zygotes and pre-implantation embryos might predict IVF outcomes more accurately than using a cumula-tive embryo score.