A process for the preparation of aqueous polymer dispersions comprising polymerizing compounds with unsaturated ethylenic bonds at a temperature of 10.degree. to 100.degree. C. in the presence of an at least partially water-soluble free-radical initiator and at least one starch and/or starch derivative and optionally present conventional adjuvants with the starting mixture containing not more than one third of the total monomers and the remaining monomer being added during the polymerization, the initiators being at least one member of the group consisting of hydrogen peroxide, ketone peroxides and organic hydroperoxides in an amount of at least 30 mmol per kg of total monomer mixture and optionally present water-soluble reducing agents and the starch is water-soluble or gells in water and contains not more than 30% by weight of amylose and the starch derivative is hydrolyzed starch in an amount of at least 0.6% by weight based on the total monomer weight.