The principles of protection from frost damage of stone relics kept in the open is discussed. Frost damage results mainly from heaving forces in the rock during freezing, the important factor being the rate of cycling and amplitude of fluctuation of temperature. After many freeze-thaw tests on tuff blocks, the principal material used for Japanese stone relics, the authors found that more than 10 cycles of -4 to +4°C/day causes rocks to break. The possible regions in Japan where this can occur are mapped from meteorological data. Treatments to protect stone materials in these regions are recommended.