The feasibility of photocatalytic degradation of trace gaseous acetone and acetaldehyde using TiO2 supported on fiberglass cloth was studied. The results show that gaseous acetone and acetaldehyde can be completely photocatalytically degraded into CO2 and H2O, after 35 min illumination with a 375 W medium pressure mercury lamp. The effects of parameters such as the flow of reactant gases and the concentrations of oxygen and water vapor in the feed stream on the photocatalytic degradation were studied. TiO2 supported on fiberglass cloth was not easily detached. After 150 h illumination there was no significant loss of the photocatalytic activity of TiO2.