Nanosized　CdS　coupled　TiO2　nanocrystals　were　prepared　by　a　microemulsion-mediated　solvothermal　method　at　relatively　low　temperatures.　The　prepared　samples　were　characterized　by　X-ray　photoelectron　spectroscopy　(XPS),　BET　surface　area　analysis,　X-ray　diffraction　(XRD),　UV-vis　absorption　spectroscopy　(UV-vis),　transmission　electron　microscopy　(TEM)　and　high-resolution　transmission　electron　microscopy　(HRTEM).　It　was　found　that　the　CdS　coupled　TiO2　materials　consisted　of　uniform　anatase　TiO2　of　6-10　nm　with　highly　dispersed　cubic　phase　CdS　nanocrystals.　The　prepared　samples　exhibit　strong　visible　light　absorption　at　about　550　nm.　Meanwhile,　they　have　high　surface　area　in　the　range　of　156-263　m(2)　g(-1)　and　mesoporous　character　with　the　average　pore　diameter　of　ca.　5.0-6.5　nm.　The　coupling　between　the　(101)　crystal　planes　of　anatase　and　(111)　crystal　planes　of　CdS　was　observed　in　the　HRTEM　image.　Ti3+　signal　was　observed　in　the　electron　paramagnetic　resonance　(EPR)　spectrum　of　CdS　coupled　TiO2　nanocrystals　under　visible　light　irradiation.　It　provided　the　evidence　of　an　effective　transfer　of　photo-generated　electrons　from　the　conduction　band　of　CdS　to　that　of　TiO2.　As　expected,　the　nanosized　CdS　sensitized　TiO2　nanocrystal　materials　showed　enhanced　activity　in　the　oxidation　of　methylene　blue　in　water　or　nitric　oxide　in　air　under　visible　light　irradiation.　The　mechanism　of　photocatalysis　on　CdS　coupled　TiO2　nanocrystals　under　visible　light　is　also　discussed.　(c)　2005　Elsevier　B.V.　All　rights　reserved.