Permeability of granite specimens heated up to 650 ¿C were measured in the laboratory with respect to both confining and pore pressure. An unexpected behavior (permeability decrease) was found in the low temperature range (20--125 ¿C). Permeability variations are interpreted with the help of a theoretical model of porosity. Complementary measurements of porosity and absolute surface area have also been obtained. A discussion in terms of microstructural controlling parameters concludes to a decrease of crack aperture at low temperatures (20--125 ¿C), followed by an increase at higher temperatures (T>125 ¿C). ¿ American Geophysical Union 1992