BACKGROUND: Mice are fundamental models of study due to their ease of breeding, manipulation, and the well-studied genome. There has been extensive research focused on the cryopreservation of mouse germaplasm, as a way to help maintain the different transgenic mouse breeds. The first protocols for mouse sperm were developed in the 90's using slow cooling and a mixture of raffinose and glycerol. Since then, the rate of success reported remains highly variable.OBJECTIVE: The Aim of this work is to study factors that are key for developing vitrification protocols for ultra-rapid laser warming of mouse sperm.RESULTS: Our results show that due to the exquisite sensitivity of sperm cells to osmotic excursions, our target levels of dehydration (~85% water content) cannot be achieved without causing a significant decrease in sperm motility and membrane fusion.CONCLUSION: It seems likely that mouse sperm vitrification is going to be difficult to develop due to the exquisite sensitivity of mouse sperm cells to handling and dehydration.