Thermal analysis has been used successfully for the in vitro estimation of aging-related changes in biological materials, such as human erythrocytes and spermatozoa, human ear cartilage and porcine scleral tissue cells. Through low-temperature DSC curves we have observed that, as a cellular population ages, the glass-transition temperature of the overall cellular constituents (-31 degrees > T-g > -50 degrees C) shifts to higher values. Conversely, the usual procedures followed in cryobiology to improve cellular survival (i.e, procedures that use rapid freezing by vitrification in a sugar medium, like sucrose, glycerol and PPG, to reduce the amount of freezable water in the live cells) shift the T-g to lower temperatures. Thus, T-g has been shown to be a very good marker in the control of the in vitro vitality degree of a cellular population. Statistically, the cellular life-to-death curves, both for erythrocytes and spermatozoa, can be described by a cubic model.