We report the photothermal properties as well as the in vitro cell test results of titanium oxide nanotubes (TiO(2) NTs) as a potential therapeutic agent for cancer thermotherapy in combination with near-infrared (NIR) light. TiO(2) NTs are found to have a higher photothermal effect upon exposure to NIR laser than Au nanoparticles and single-wall carbon nanotubes, which have also attracted considerable interest as therapeutic agents for cancer thermotherapy. The temperature increase of a TiO(2) NT/NaCl suspension during NIR laser exposure is larger than that of a TiO(2) NT/D.I. water suspension due to the heat generated by the formation of Na(2)TiF(6). According to the in vitro cell test results the cells exposed to NIR laser without TiO(2) NT treatment have a cell viability of 96.4%. Likewise, the cells treated with TiO(2) NTs but not with NIR irradiation also have a cell viability of 98.2%. Combination of these two techniques, however, shows a cell viability of 1.35%. Also, the cell deaths are mostly due to necrosis but partly due to late apoptosis. These results suggest that TiO(2) NTs can be used effectively as therapeutic agents for cancer thermotherapy due to their excellent photothermal properties and high biocompatibility.