In a process for the two-stage catalytic gas-phase oxidation of propene to acrylic acid, the reaction gas starting mixture is passed, in a tube-bundle reactor, with a propene loading of ≧160 l (S.T.P.) of propene/l·h, first over a fixed catalyst bed 1 present in two successive temperature zones A, B and then over a fixed catalyst bed 2 which is housed either in one further temperature zone C or in two further temperature zones D, E, the temperature of the zone A being kept at a lower temperature than the zone B and the temperature of the zone D at a lower temperature than the zone E.