Titanate nanotubes were prepared by hydrothermal treatment of anatase TiO2 with concentrated NaOH solution. In situ synchrotron X-ray diffraction studies revealed that the nanotubes are thermally unstable at temperatures above 360 degrees C and can transform directly to anatase via a dehydration and recrystallization process. This indicated that the titanate nanotubes possess an orthorhombic lepidocrocite (gamma-FeOOH)-type layered structure. An aggregate of the as-prepared nanotubes showed an electric conductivity of about 1 x 10(-6) S cm(-1) at 50 degrees C in humid atmospheres. The conductivity depended on humidity of the atmosphere and decreased with increasing temperatures, suggesting that the proton conduction in the titanate nanotubes might correlate with the interlayer H3O+ ions.