Isolating thermoplastic or thermoelastic polymers in the form of a powder of limited water and precipitant content and uniform grain size from their aqueous dispersions wherein(i) a polymer dispersion and a precipitant are intensively mixed at an uptake of mechanical energy of 0.2 to 0.6 KWh per m.sup.3 of dispersion thus causing high turbulence,(ii) the polymer is precipitated while in this state of high turbulence at a temperature below the sintering temperature of the polymer,(iii) the precipitated polymer particles are agglomerated and hardened while still in contact with the aqueous liquor either in one or in several stages, and(iv) the aqueous liquor and agglomerated polymer particles are separated from one another.