The objectivess of this study were the determination of the second-order rate constants for the reactions of permanganate and chlorine with microcystin-LR (MC-LR) and cylindrospermopsin (CYL), and the formulation of a kinetic model to predict the toxin removal in drinking water treatment. Second-order rate constants for the reactions of MC-LR and CYL with permanganate and chlorine were determined in experiments performed in large excess of oxidant (first-order conditions). The experiments started after addition of an aliquot of a concentrate stock oxidant solution to a buffered toxin solution (10 mL). At fixed time intervals, 0.5 mL of sample was rapidly transferred with a syringe into a HPLC vial containing tiosulphate to stop the reaction. The concentration of residual MC-LR and CYL was analyzed directly by HPLC. The elimination of MC-LR in surface water (pH=7.3, DOC=5.6 mg/L, [bicarbonate]=2.4 mM, [ammonia]=3.2 mM) was also investigated. Experiments were run with different initial oxidant doses, pH and temperature, covering well the conditions found in full-scale drinking water treatment. The initial MC-LR was very low (5 mg/L) as it is found in real samples. Experiments were performed by adding an aliquot of oxidant solution to the buffered natural water containing MC-LR. For each desired reaction time, oxidant and MC-LR concentrations were analyzed. In these experiments, MC-LR concentration was measured by HPLC after SPE enrichment. Includes 5 references, figures.