Abstract: Disclosed is a method of freezing bulky biological material, comprising transferring heat out of said material to cool the material and increasing the rate of heat transfer during a time period when the inner portion of said biological material freezes and releases latent heat. This method allows prolonged ex-vivo preservation of solid mammalian organs, including a liver or significant portion thereof and a heart. The invention also provides a bank of deposited body organs or tissues as well as methods for operating such a bank.