This study was carried out to establish an effective embryo production system by analyzing several factors ifluencing in vivo embryo production in Hanwoo. The results are summarized as follows : 1. The number of total, fertilized and transferble embryos by gonadotropins were no significant difference among PMSG, FSH and FSH+PMSH. 2. The numbers of recovered and transferable embryos by type of FSH were no significant difference in both FSH-P and FOLLTROPIN-V but significant difference with SUPER-OV(p<0.01). 3. The numbers of recovered and transferable embryos by age of donor were highest in 5 years old. 4. The recovered number of transferable embryos was highest in the cows at the 1 st and 3rd parity but significantly lower in hifers and the cows at more than 6th parities(p<0.01). 5. The numbers of trasferable embryos by postparient were more<270 days than > 270 days in significant difference(p<0.01). 6. Embryo production after treatment of repeated super ovulation was no significant difference. 7. Recovered and trasferable embryos production after treatment of repeated super ovulation interval was highest 81∼100 days and significant difference(p<0.01). 8. The numbers of recovered and transferable embryos by seasons were no significant difference.