Ultrahigh crystalline TiO2 nanotubes were synthesized by hydrogen peroxide treatment of very low crystalline titania nanotubes (TINT-as prepared), which were prepared with synthesized TiO2 nanoparticles by hydrothermal methods in an aqueous NaOH solution. Thus, prepared ultrahigh crystalline TiO2 nanotubes (TINT-H2O2) showed comparable crystallinity with high crystalline TiO2 nanoparticles. The details of nanotubular structures were elucidated by high resolution-transmission electron microscopy (HR-TEM), field emission-scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis in transmission electron microscopy (TEM-EDX), X-ray diffraction (XRD), photoluminescence (PL), and BET surface area. TINT-H2O2 was found to be a multiwalled anatase phase only with an average outer diameter of similar to 8 nm and an inner diameter of similar to 5 nm and grown along the [001] direction to 500-700 nm long with an interlayer fringe distance of ca. 0.78 nm. The photocatalytic activity of TINT-H2O2 was about 2-fold higher than those of TINT-as prepared, synthesized TiO2 nanoparticles, and TiO2-P25 (Degussa) in the photocatalytic oxidation of trimethylamine gas under UV irradiation.