Interactions of hydrogen with the interface formed between ZrO2 and zirconium suboxide (ZrOx, x < 2) were studied on a 10 Angstrom zirconium oxide film prepared on gold foil for X-ray photoelectron spectroscopy (XPS) analysis. This film was subject to a set of sequential treatments. Reaction with II, gas at 2 mbar pressure and room temperature indicates that the ZrO2/ZrOx interface appeared to undergo a redox-type reaction and convert to a new ZrO2/ZrOy (x < y < 2) film. Heating this structure at 300 degrees C in a 10(-9) mbar vacuum (residual gas dominantly H2O) resulted in more ZrO2 in the outer region and less ZrO, in the subsurface. By contrast, when this film was treated with a hydrogen plasma, XPS showed enhanced formation of -OH groups and complete conversion to the ZrO2-like form. On heating to 300 degrees C, this uniform film regenerates the ZrO2/ZrOy interface structure, apparently with desorption of H2O.