Low concentrations of acetaldehyde in air (60 ppm) were oxidized over TiO2 (Degussa P25) and 0.5% Pt/TiO2 catalysts from 24 to 200 degrees C by photocatalytic and thermal catalytic reactions. On Pt/TiO2, the contribution by photocatalytic oxidation (PCO) is a maximum at 140 degrees C, where conversion is 2.8 times that at 24 degrees C. Titania without Pt deactivates rapidly during PCO at elevated temperature due to a thermal catalytic reaction that takes place in parallel with PCO, but the addition of Pt dramatically slows deactivation. Apparently, Pt supplies spillover oxygen onto the TiO2, and the oxygen oxidizes the acetaldehyde decomposition products in a dark reaction. Deactivated TiO2 without Pt was regenerated by PCO at room temperature. Seven distinct reactions (photocatalytic and thermal catalytic) are identified on Pt/TiO2.