The photoactivated degradation reaction of rhodamine B (RB) was studied using P-25 TiO2 (Degussa) as catalyst. Three process variables – temperature, initial pH, and catalyst concentration – were evaluated. Temperature had a slight effect on reaction rate; however, the combined effect of pH and catalyst concentration was greater. pH affected the catalyst particle’s adsorption of RB, altering the reaction rate. The concentration of the catalyst was significant only up to 0,65 g L-1. The effect of temperature was studied at optimum pH and 50ºC was found to be the optimum operational temperature. The effect of the presence of a surfactant (sodium dodecylsulfate, SDS) and ionic contaminants (Cl- and SO4 --) in the reaction system was also studied. The surfactant improved the catalyst’s adsorption of RB by more than 80%, increasing the degradation reaction rate as well. The ionic contaminants reduced the reaction rate.