Cryopreservation of organs of large mammals and humans is a complicated task. In order for organs to be cryopreserved, cryoprotective agents (CPAs) must be introduced into the organ. The best way for doing that is by vascular perfusion. Cryopreservation of samples of large volume (i.e. tissues, organs, or large volumes of semen) is associated with heat and mass transfer problems that are distinct from those associated with an isolated cell model. Cryopreservation of whole ovaries, using the directional freezing technology combined with microvascular anastomosis, is a very promising method for preserving long-term reproductive capacity and endocrine function. One of the most difficult issues for patients needing organ transplants is the narrow time window needed between the donation and transplantation of the donated organ. The situation is complicated by the logistical challenges of handling these life-giving donations and maintaining organ viability until the time of transplant.