A series of mesoporous titanium dioxide microspheres were calcined at various temperatures to improve their photocatalytic activity. The prepared catalysts were characterized by XRD, SEM, TEM, TG-DTA, UV-vis, and N(2) adsorption-desorption measurements, and their photocatalytic performances were investigated by photooxidation of gaseous toluene. As the results revealed, calcination temperatures obviously influenced the surface morphology and photocatalytic activity of the mesoporous TiO(2) microspheres. The noncalcined samples had a mesoporous structure of the anatase phase. The sample calcined at 400 °C showed a superior photocatalytic performance, which had a reaction rate constant 2-fold higher than that of P(25). The enhanced photoreactivity is possibly due to the synergetic effects of the mesoporous structure and light-transmittance ability of the catalysts. Two new reaction intermediates were discovered as well, and a tentative degradation pathway was proposed.