Biological materials in both cryopreservation and cryosurgery are composed of various chemicals and experience a wide range of temperature change. Therefore, their thermal properties including specific heat, latent heat (including water/ice and eutectic phase change) and thermal conductivity are expected to change significantly during freezing/thawing. The effects of thermal properties on heat transfer in cryopreservation/cryosurgery were studied experimentally and numerically. Thermal properties of various biological aqueous solutions were measured over a wide temperature range (-150-30°C). To estimate the effect of thermal property changes on the heat transfer, numerical simulations of both cryopreservation (cooled from outside) and cryosurgery (cooled from inside) geometries were performed with constant and temperature-dependent properties. The results show that the constant-property case significantly under-predicts the heat transfer over the temperature-dependent-property case regardless of the geometry.