An improved process for the production of acrolein from propylene and of acrylic acid from propylene or acrolein or mixtures of propylene and acrolein which essentially comprises catalytic oxidation of propylene and/or acrolein with oxygen or a gas containing molecular oxygen in the presence of an oxidation catalyst and of methanol in a quantity of from 0.01 to 1% by volume with respect to the total gaseous mixture of the reactants. Acrolein and acrylic acid are formed in the process at high conversion rates and selectivities.