The degradation of gibberellic acid (GA(3)) from aqueous solution has been carried out by the different oxidation processes: UV, UV/H2O2, Fenton and photo-Fenton processes. The effect of operating parameters such as Fe2+, H2O2 concentrations, UV-A light intensity and initial pH was studied. It is possible to create a strongly irradiated region along the axis of cylindrical photochemical reactor throughout the photo-Fenton process. The increased intensity of UV-A light due to the degradation and mineralization of GA(3) during the photo-Fenton process was explored. The highest GA(3) removal efficiency was achieved at 0.08 mM/1 mM Fe2+/H2O2 at pH 3 for Fenton processes. The removal efficiencies of GA(3) and TOC were 60 % and 5 %, respectively. GA(3) degradation was completed and 16% TOC removal was achieved by the photo-Fenton process at 45 x 10(-6) Einstein s(-1) UV-A light intensity. The kinetics of degradation and mineralization were found to follow first-order reaction rules in both processes.