Preparing pigment preparations by mixing a dyestuff with a monomer and simultaneously polymerizing the monomers in an extruder at elevated temperatures, wherein the following steps are carried out: (A) introducing continuously into an extruder (a) from 40 to 90% by weight of a pigment, (b) from 60 to 10% by weight of a monomer or a monomer mixture, and (c) from 0.01 to 10% by weight, related to the amount of monomer component (b), of an initiator or a mixture of initiators, and (d) from 0 to 10% by weight, related to the amount of monomer component (b), of a chain transfer agent, whereby the amounts of the pigment and the monomer or monomer mixture sum up to 100%, and whereby the monomer component (b) is admixed with either the initiator or mixture of initiators (c), or the chain transfer agent (d), or the initiator or initiator mixture (c) and the chain transfer agent (d), before it is introduced into the extruder, (B) simultaneously mixing the components (a) to (c), as well as (d) if present, and polymerizing the monomer or copolymerizing monomer mixture within the extruder, and (C) withdrawing continuously the obtained reaction mixture from the extruder, pigment preparations, high molecular weight organic material pigmented therewith as well as the method of use thereof.