Transparent　zeolite-like　mesoporous　TiO2　nanocrystalline　thin　films　with　high　photocatalytic　activity　were　synthesized　via　a　surfactant-templated　method.　The　films　were　characterized　by　TGA-DTA,　XRD,　nitrogen　adsorption,　SEM,　TEM,　UV/vis,　and　FT-IR　spectroscopy.　The　photocatalytic　activity　of　the　films　was　evaluated　by　photodecomposition　of　acetone　in　air　at　ambient　conditions.　It　was　found　that　thermal　treatment　resulted　in　surfactant　elimination,　framework　solidification,　as　well　as　pore-wall　crystallization　of　the　mesoporous　TiO2.　The　resulting　zeolite-like　mesoporous　TiO2　nanocrystalline　films　had　large　specific　surface　areas　(∼-100　m2/g),　high　porosity　(∼40%),　extended　band　gap　energy　(∼3.3　eV),　tridirectional　communicating　pore　systems,　and　enhanced　photocatalytic　activity.　The　optimum　calcination　temperature　was　found　to　be　500　°C,　at　which　the　film　possessed　a　cubic　ordered　mesoporous　structure　and　exhibited　the　highest　photocatalytic　activity.　A　comparison　with　a　conventional　TiO2　film　(prepared　from　a　sol-gel　method)　showed　that　the　ordered　mesoporous　TiO2　nanocrystalline　film　(calcined　at　500　°C)　had　over　2　times　the　specific　photocatalytic　activity　as　the　conventional　film.　The　high　photocatalytic　activity　of　zeolite-like　mesoporous　TiO2　thin　films　can　be　explained　by　the　large　specific　surface　area　and　the　three-dimensionally　connected　mesoporous　architecture.