Solid-base catalysts consisting of CaO covered with 5-20 mol% TiO2 (TiO2/CaO) were prepared by deposition of titanium tetraisopropoxide (Ti(OCH(CH3)(2))(4)) on a Ca(OH)(2) surface in an ethyl acetate solution, followed by thermal decomposition in air at 773-1073 K for 3 h. The catalyst heated at 773-973 K showed higher activity for the base catalyzed retro-aldol reaction to convert diacetone alcohol (4-hydroxy-4-methyl-2-pentanone) to acetone at 299 K. 10 mol% TiO2/CaO heat-treated at 773 K was the most active catalyst for the retro-aldol reaction among the metal oxide -covered CaO catalysts. The catalyst treated at 1073 K was inactive for the same reaction, as was uncovered CaO. The catalytic activity of TiO2/CaO poisoned by water was recovered by washing with acetone, confirming that TiO2-covered CaO had sufficient stability against H2O. No leaching of Ca2+ into the polar solvent diacetone alcohol was observed in any covered catalyst.