A steady-state photolytic investigation using TiO2 as the photocatalyst in its reaction with uracil, thymine, 6-methyluracil and cytosine in an aqueous suspension has been carried out. Influence of initial [cytosine], amount of TiO2 added and pH on the reaction rate and Phi were evaluated. The photoprocess obeys the Langmuir-Hinshelwood isotherm. Fe3+-doped TiO2 prepared by the impregnation method was found to have a modified photocatalytic activity in the photooxidation of all the above-mentioned pyrimidine bases. The effect of calcination (preheat treatment) of the TiO2 photocatalyst was a rate retardation. The role of these parameters on surface properties of TiO2 is suitably explained.