The authors conducted freeze-thaw experiments on specimens of tuff occurring in Tochigi prefecture. These were treated with or without (as control) silicone, epoxy or acrylic resin for preventing from breaking in the following four ways: a) applying the resin solution to the specimen by a brush; b) soaking the specimen with the resin solution for 10 minutes; c) soaking for 60 minutes; d) soaking for 18 hours. Each specimen was measured for compressive strength, tensile strength, ultrasonic velocity, porosity (volume percent of pores communicating with theopen air which can be replaced with water) and saturated water content (abbreviated as SWC). The compressive and tensile strengths of all the treated specimens were not significantly different from those of the control, indicating that appreciable hardening effect did not result from the treatment with the resins used. Porosities and SWC of the specimens treated with silicone resin decreased, showing greater extent of the decrease in latter way of treatment of the above four ones a) to d). Those treated with either acrylic or epoxy resin were not significantly different from the control in both values. In the test of freeze-thaw cycle (a cycle of the temperature change between -10 and 20 C per day is repeated for 20 days in total), most of the specimens were damaged after 10 cycles except those treated with silicone resin, showing greater resistance to breaking the longer they were soaked. The broken specimens showed the increase in porosity and the decrease in ultrasonic velocity but the unbroken specimens did not significantly change in both values. The effect of the treatment with a resin can be evaluated by the porosity and SWC and porosities lower than 20% and SWC lower than 0.1 after the treatment can be expected to be sufficient to prevent a stone from breaking by freezing. The mechanism of the damage of stones by freezing is discussed. See also AATA 20-2069.