The effects of various cryoprotectants namely dimethyl sulfoxide, methyl alcohol, ethylene glycol, glycerol, erythritol, adonitol and xylitol on the survival of frozen-thawed mouse embryos were examined. The effects of the different developmental stages of embryo and the dilution methods of cryoprotectant, were also examined. The cryoprotectant was added to the embryos in 5 equal increments 5 minutes apart, giving a final concentration of 1.5 M. The embryos were frozen with a programmable freezer, and then stored in LN₂.<BR>Rapid thawing was done by placing the straws in 37°C water. The cryoprotectants were diluted from the embryos in one of the two ways: (a) embryos were pipetted into phosphate buffered saline (PBS) containing 0.5 M sucrose and were kept there for 5 minutes before transferring them into PBS (sucrose method), or (b) directly pipetting them into PBS (PBS method).<BR>In this study, ethylene glycol, glycerol and DMSO were found to be more effective as compared to methyl alcohol and adonitol as cryoprotectants. With the use of erythritol or xylitol, the embryos can survive only when the sucrose method was carried out. However, the embryos can survive with both dilution methods when ethylene glycol was used.