The photothermal therapy using nanomaterials has been recently attracted as an efficient strategy for the next generation of cancer treatments. Single walled carbon nanotube (SWNT) is an upcoming potent candidate for the photothermal therapeutic agent since it generates significant amounts of heat upon excitation with near-infrared light (NIR, lambda = 700-1100 nm) which is transparent to biological systems including skins. Such a photothermal effect can be employed to induce thermal cell death in a noninvasive manner. Here, we demonstrate in vivo obliteration of solid malignant tumors by the combined treatments of SWNTs and NIR irradiation. The photothermally treated mice displayed complete destruction of the tumors without harmful side effects or recurrence of tumors over 6 months, while the tumors treated in other control groups were continuously grown until the death of the mice. Most of the injected SWNTs were almost completely excreted from mice bodies in about 2 months through biliary or urinary pathway. These results suggest that SWNTs may potentially serve as an effective photothermal agent and pave the way to future cancer therapeutics.