A laboratory program to study the effects of temperature up to 350 °C on the strength and deformation properties of rocks was carried out. Particular attention was paid to the experimental procedure to avoid premature thermal cracking of the specimens. It was shown that the thermal–mechanical behaviour varies with the rock type. For granitic gneiss, the deformation modulus increases slightly with temperature up to 120 °C, then decreases at a rate of about 25% per 100 °C. Poisson's ratio generally decreases with increasing temperature up to 250 °C. The uniaxial compressive strength of granitic gneiss decreases with increasing temperature at a rate of the order of 30 MPa per 100 °C. The deformation properties of the granitic gneiss are also dependent on the temperature history of the specimen.In contrast, both the deformation and strength behaviour of the limestone appear to be insensitive to temperature change.