Diffusion from a metallic gold source into SiO2films on (100) silicon substrates at 1000 °C for 15 min leads to large negative shifts in theC‐Vcurves and distortion of theC‐Vcharacteristics. Annealing in hydrogen in the temperature range 300–450 °C, in argon at 1100 °C, or short exposure to steam at 950 °C is only partially effective in reversing these changes. Gold from a metallic source appears to diffuse in SiO2mostly or exclusively as metallic gold and to cause the generation of a very large density of interface states. Most of the negativeC‐Vshift is due to these interface states and not due to a laterally uniform fixed oxide charge, as claimed by other researchers. The magnitude of the effect depends in thethickness of the gold film, and hence directly or indirectly on the amount of gold diffused into the SiO2film because thicker gold films result in larger amounts of gold diffusion in uniform fashion into the SiO2. The total amount of gold in the SiO2film after diffusion, however, is insufficient by several orders of magnitude to account, on a one‐to‐one basis, for either the supposed oxide charge or the interface‐state density. It must be concluded that gold diffusion in SiO2films leads to the formation of interface states by an entirely new and unexplained mechanism.