introduction: determination of best culture medium for fertilization and development of nmri mice. material and methods: development of fertilized mature oocytes of nmri mice was studied for five days in several culture media (ksom, t6, m16, czb, g1tm ver3 and g2tm ver3) following hormone therapy with pmsg and hcg. results: the rate of fertilization after 24 hours was 97.4% in ksom, 83.5% in t6...