Abstract: A newly discovered property of thermal hysteresis proteins is the interaction of these proteins with cell membranes and thus with cells themselves, protecting cells and their membranes from damage which they would otherwise suffer upon exposure to non-physiological conditions such as temperature abnormalities, including both hyperthermic, hypothermic and sub-freezing temperatures. Improved rates of cell viability are observed over a wide range of conditions which do not involve ice formation, including temperatures above the freezing range as well as temperatures below the freezing range but in vitrification conditions. Heretofore the only known property of these proteins was their ability to interact with ice crystals.