We report the hydrothermal synthesis of vertically aligned, multiwalled trititanate (H2Ti3O7) nanotube arrays self-assembled on oxidized titanium foils. The growth mechanism is studied in detail using high resolution electron microscopy. We show that a Ti-rich core layer acts as a substrate for the growth of the trititanate nanotube array, whereas the surrounding oxide (rutile) layers serve as the source material. Upon annealing at 500 °C, the 1-D array morphology remains unchanged, but the hollow nanotubes of hydrogen titanate get converted to solid nanorods of TiO2-B, a lowdensity titania polymorph. One dimensional arrays of both H2Ti3O7 and TiO2-B are expected to find applications in lithium ion batteries, solar cells, hydrogen sensors, and hydrogen storage and as active catalysts. We provide a straightforward synthesis technique for vertically aligned 1-D arrays of both systems, with excellent adherence to the Ti-rich substrate. © 2010 American Chemical Society.