During the last years, many laboratory experiments have been carried out to study electrical properties of rock samples subjected to temperature, hydrostatic pressure and internal pore fluid pressure cycles. For the experiments an "ad hoc" apparatus has been designed at Applied Geophysical Laboratory of University of Florence, that can condition temperature (up to 300 ·C), hydrostatic pressure (up to 40 MPa) and internal pore fluid pressure (up to 40 MPa).