The nature of surface hydroxyls present in the native air-formed oxide film on titanium has been studied by X-ray photoelectron spectroscopy (XPS), variable angle XPS, and secondary ion mass spectroscopy (SIMS). The surface isoelectric point of the oxide film on titanium is 5.0, as determined from XPS measurements; and the concentration of surface hydroxyl groups on oxide-covered titanium is 10 OH groups/nm(2), as determined by quantitative XPS.