Abstract Tunneling through an oxide barrier into amorphous silicon was investigated between liquid nitrogen and room temperatures. The tunneling junctions consisted of platinum, silicon oxide, and amorphous silicon in a sandwich configuration. The tunneling conductance, obtained by electronic differentiation, was found to be nearly symmetrical in bias voltage and to increase smoothly from zero bias. The observed temperature dependence of the tunneling conductance is interpreted in terms of localized states within a mobility gap. A mobility gap of approximately 1.6 eV and a density of localized states at the Fermi level of about 10 20/eV·cm 3 are inferred from the conductance data.