The effect of incorporation of SiO2 on the behavior of a TiO2-based photocatalyst prepared by a sol-gel technique from organometallic precursors is described. Application of photocatalysts with different TiO2/SiO2 ratios to the photodecomposition of rhodamine-6G (R-6G) demonstrates that a ratio of 30/70 produces a catalyst about 3 times more active than Degussa P-25 TiO2. Larger amounts of SiO2 decrease the activity. The adsorption of R-6G on the different materials and the photodecomposition of preadsorbed R-6G is also described. The studies suggest that photogenerated intermediates are sufficiently mobile to react with R-6G adsorbed on SiO2 sites but that adsorption of R-6G on TiO2 is not a prerequisite for reaction.