Abstract: A catalyst according to the present invention for di-, oligo-, co- and poly- merization of vinyl monomers consists of an active phase comprising a compound of a transition metal of Groups IV-V of the periodic system deposited onto a polymeric carrier, viz, a macroporous copolymer of vinyl and divinyl monomers with a specific surface area of 30 to 700 m.sup.2 /g and a co-catalyst such as an organo-aluminum compound. The catalyst according to the present invention makes it possible to obtain dimers in high yields of more than 6,000 kg as calculated for 1 g of the transition metal for 2 hours and polymers in yields of up to 72 kg per 1 g of the transition metal. The catalyst according to the present invention makes it possible to control the particle size of the resulting (co) polymer which enables the use of the (co) polymer avoiding the stage of granulation.