In vitro fertilization of mouse and hamster eggs after freezing and thawing.

Mouse eggs (12-14%) and hamster eggs (87-94%) appear normal upon thawing after having been stored for 30 min to 25 h at -70 degrees C and -196 degrees C. While 89-98% of the normal appearing hamster eggs are capable of fertilization in vitro, only 4-13% of the mouse eggs can be fertilized. The ability of fertilized eggs to develop in culture and their viability upon transfer to pseudopregnant recipients is under investigation.