Disclosed is a simplified process for producing magnetic polymer particles. The process comprises: (a) providing a composition having a liquid monomer which is radical polymerizable, a radical initiator soluble in the monomer, a steric stabilizer, and a ferrofluid comprising surfactant-coated colloidal magnetic particles in a carrier fluid which is miscible with the monomer; (b) preparing an emulsion from a polar solvent which is immiscible with the monomer, and the composition of step (a); (c) adding seed polymer particles to the emulsion, mixing to form a seeded emulsion, and incubating the seeded emulsion, thereby swelling the seed polymer particles; and (d) activating the radical initiator and polymerizing the monomer in the swollen seed polymer particles; thereby producing the magnetic polymer particles. The process forms monodisperse magnetic particles. The particles are characterized by a uniform distribution of magnetic material, and an absence of magnetite bleeding.