The electrical (volume conductivity) and dielectric (loss factor and dielectric constant) properties of glass-ceramics belonging to the CaO-MgO-Al2O3-SiO2 system have been studied, as a function of microstructure, in their glassy and ceramized forms on samples obtained as bulk materials or sintered powders. A possible application of these materials as substrates for electronic devices can be envisaged, on account of their low conductivities (<10(-14) Scm(-1) up to 250 degrees C), loss factor and permittivity values.