Sharing genetically modified mouse models is a very important part of collaboration between researchers. Shipping live animals around the world is inconvenient, expensive, and cumbersome because of the variety of international regulations and paperwork. The issue of health status differences between animal facilities is of great importance; traditionally, imported animals are quarantined to determine their health status and avoid the introduction of undesirable pathogens. The shipment of preimplantation-stage embryos for immediate transfer into pseudopregnant recipients upon arrival is a commonly used method for transportation. Time coordination on both sides is critical in this case, but the shipment can be done by any courier and the container does not need to be returned. This protocol has been used since the early 1990s to rederive dozens of mouse strains.