The epoxidation of an cy-keto olefin, cx-isophorone, has been studied using high-surface-area, amorphous titania-silica aerogels. The mixed oxides were prepared by the alkoxide-sol-gel route and the solvent was removed by semicontinuous extraction with supercritical CO2. The morphology of the catalysts was studied by HRTEM. The influence of the following reaction parameters was investigated : temperature, the chemical nature of hydroperoxide and solvent, and the ratio of olefin to catalyst or peroxide. The highest reaction rate and selectivity were obtained in alkylaromatic solvents of low polarity. Polar solvents compete for the active coordination sites and lower the reaction rate. All tested aerogels provided high epoxide selectivity (98-100%) at 333 K, using t-butyl hydroperoxide as oxidant in an olefin:peroxide molar ratio of 5:1. No epoxide formation was observed with H2O2. A considerable leaching of titanium in the aqueous oxidizing medium (evidenced by FTIR and ICP-AES analysis) is attributed to the hydrolysis of the Ti-O-Si bonds. The aerogels containing 20 or 2 wt% TiO2 show the highest rate, related to the amount of catalyst or TiO2, respectively. There is a positive correlation between oxidation rate and Ti-O-Si connectivity, characteristic of Ti-dispersion in the silica matrix. The suppressed reactivity of Lu-isophorone compared to cyclohexene is attributed to the electron-withdrawing effect of the carbonyl group, whereas the influence of the 2-methyl group (steric hindrance and electron release) is of secondary importance. The best titania-silica aerogel proved to be superior to TiO2-on-SiO2, TS-1, and titania-silica xerogels.