Organ preservation is the supply line for organ transplantation. Currently, the liver, pancreas, and kidney can be successfully preserved for up to two days by flushing the organs with the University of Wisconsin (UW) organ preservation solution and storing them at hypothermia (0-5 degree C). The UW solution is effective because it uses a number of cell impermeant agents (lactobionic acid, raffinose, hydroxyethyl starch) that prevent the cells from swelling during cold ischemic storage. Additionally, the UW solution contains glutathione and adenosine, agents that may stimulate recovery of normal metabolism upon reperfusion by augmenting the antioxidant capacity of the organs (glutathione) or by stimulating high-energy phosphate generation (adenosine) upon reperfusion. Although this method of organ preservation is effective, some organs (5-15% of livers and 20-30% of kidneys) do not function well upon transplant. Injury may be preservation related but may also result from donor and recipient factors that render the organs more susceptible to preservation damage. Results with continuous perfusion of kidneys in the clinics show a reduction in preservation/reperfusion damage. This may be a more appropriate preservation method than cold storage. In this chapter we discuss the development and use of the UW solution and present clinical results. Although intraabdominal organs are well preserved at present, intrathoracic organs (lungs and heart) are less well preserved, and better methods for preservation of these organs are needed for increased use of lung and heart transplantation.