Laser Raman spectroscopy (LRS), X-ray di4raction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet and di4use re6ectance spectroscopy (UV-DRS), and temperature-programmed reduction (TPR) are used to characterize a series of TiO 2 / -Al 2 O 3 , NiO/ -Al 2 O 3 , and NiO/TiO 2 / -Al 2 O 3 samples. For TiO 2 / -Al 2 O 3 samples, LRS results indicate that the dispersion capacity of titania on -Al 2 O 3 is about 0.62 mmol 100 m ؊2 -Al 2 O 3 , which is slightly higher than the theoretical value (0.56 mmol 100 m ؊2 -Al 2 O 3 ) calculated by the consideration of the incorporation model (Y. Chen and L. F. Zhang, Catal. Lett. 12, 51 (1992)). At low TiO 2 loading, 40.62 mmol 100 m ؊2 --Al 2 O 3 , only highly dispersed titania species are found on the surface, possibly due to the incorporation of the dispersed Ti 4؉ ions into the surface vacancies of -Al 2 O 3 . Increasing the loading amount of titania leads to the formation of crystalline TiO 2 besides the surface-dispersed titania species. The results show that the state of titania is related to its loading on -alumina. The results of XRD and UV-DRS show that the dispersion capacity of NiO on titania-modi5ed -Al 2 O 3 is lower than that of NiO on -Al 2 O 3 , which is probably caused by the decrease of the useable surface vacancies on -Al 2 O 3 due to the incorporation of the Ti 4؉ ions. TPR results of NiO/ -Al 2 O 3 and NiO/TiO 2 / -Al 2 O 3 samples reveal that the reduction behaviors of NiO dispersed on -Al 2 O 3 and on titania-modi5ed -Al 2 O 3 are apparently di4erent. This result emphasizes that the surface structure of the support is important to the properties of the dispersed metal oxide species. The coordination environments of the dispersed titania and nickel oxide species are discussed on the basis of the incorporation model proposed previously.