Preparation of Ce/TiO(,2) (anatase) by sol-gel method was presented as an example in control of molecularscale mixing to produce active metal oxide phase suitable for catalysis. The relative activities ofprecursor hydrolysis and condensation were proved to dictate the structure of gel network in formingCe/TiO(,2) (anatase) after calcination. The prepared gel from low mole ratio of water to titaniumprecursor [titanium(IV)bis(ethyl acetoacetato)diisopropoxide] exhibited mainly active anatase phase ofTiO(,2). Cerium ion on TiO(,2) (anatase) was produced from the cerium nitrate which was readily hydrolyzedand the condensation reactivity was different from the titanium precursor. It incorporated in anatasestructure as an interstitial species, causing the distortion of axial Ti-0 bonds in the unit cell,whereas heterocondensation between different hydrolyzed alkoxides occurred when cerium acetylacetonatewhich the hydrolysis and condensation rates are the same as that of titanium precursor was used. Thiscaused the formation of Ce-O-Ti bonds in anatase structure and cerium titanium oxide compound as aresult. Catalytic activity of the prepared catalysts in toluene oxidation studied by ~iin situ~i DRIFTSindicated that active site of Ce/TiO(,2) catalysts was Ce-O-Ti bonds existing in anatase phase. With highloaded cerium species (30%Ce/TiO(,2)), the catalyst showed the lower activity than that of the low loadedcerium species (8%Ce/TiO(,2)) due to the decrease of anatase crystallinity. The catalyst prepared by ceriumacetylacetonate displayed a superior performance for toluene oxidation than the catalyst prepared bycerium nitrate due to the high amount of Ce-O-Ti bonds presented in anatase phase. The effect of highwater content used in the sol-gel process on the structure of Ce/TiO(,2) catalysts caused the brookitephase formed in the poorly crystalline anatase and resulted in the low catalytic activity of catalyst.