The thermal expansivity and isothermal compressibility atp=0 of solid rare gases can be measured interferometrically in the temperature region between 2° and 150°K. The experimental errors are about 1% in the whole temperature region. First measurements have been done on solid Kr. We have found that the volume thermal expansion coefficient varies from (3.80±0.02)×10−5°K−1at 5°K to (1.82±0.012)×10−3°K−1at 115°K (triple point). The isothermal compressibility atp=0 varies from (2.93±0.022)×10−11dyn−1cm2at 5°K to (8.83±0.10)×10−11dyn−1cm2at 115°K.