In this paper it is demonstrated unequivocally by solid-state nuclear magnetic resonance and diffuse reflectance infrared Fourier transform spectroscopies that, at high temperature, hydrogen reacts directly with pyrogenic silica to form stable hydride Si-H groups. Such modified silicas should exhibit specific properties far from those of silicas having only surface silanol groups. The interest for hydride-modified silicas arises from the possibility of using their Si-H groups as reducing agents or as active sites for the synthesis of new chromatographic phases.