The mechanistic investigation of oxidation of levofloxacin (LF) has been studied by chloramine-T(CAT) in aqueous perchloric acid medium at 25 degrees C. The reaction followed first-order kinetics with respect to [CAT], [LF], and [H+] in their lower concentrations range, tending to zero-order at their higher concentrations. First-order kinetics with respect to [CAT] was observed for the oxidation of levofloxacin. An increase in perchloric acid concentration increased the rate of reaction. The effect of added products, ionic strength, and dielectric constant of the medium was studied on the rate of reaction. The main products were identified by spot test, FT-IR, and NMR. A mechanism was proposed on the basis of experimental results. The activation parameters with respect to the slow step of the mechanism was evaluated, and the thermodynamic parameters were also determined and discussed.