A kinetic model has been developed for the heterogeneously catalyzed methacrolein oxidation, the parameters of which reflect the redox and adsorptive properties of the heteropolyacid catalysts CsxH3-x+y[PMo12-yVyO40] (x = 0, Y = 0, 1; x = 1, Y = 0, 1, 2). The model based on the Mars-van Krevelen mechanism describes the reaction rates of methacrolein and oxygen consumption as well as the rate of methacrylic acid and byproduct formation as a function of the methacrolein and oxygen partial pressures. Substitution of Mo by V causes a strong decrease of tl-Le ratio of reaction rate constants of reoxidation and methacrolein oxidation. The substitution of Mo by V leads to a strong decrease of the rate of consecutive methacrylic acid oxidation. Salification of the free acid by cesium provides a decrease of byproduct formation via parallel and consecutive oxidation and also a reduction of the hindrance of catalyst reoxidation caused by strong adsorption of methacrolein.