AbstractThe number of propagation centers (Cp) and the propagation rate constant (Kp) in the polymerization of ethylene and propene in the presence of heterogeneous TiCl3 derived Ziegler‐Natta catalysts of different composition were determined using the method of quenching the polymerization by radioactive carbon monoxide (14CO). The values of Kp, (1,2±0,3)·104 l mol−1 s−1 at 75°C for ethylene and (90±20) l mol−1 s−1 at 70°C for propene polymerization, significantly exceed those ones obtained by use of tritium tagged alcohols as quenching agents. Further, for the polymerization of olefins in the presence of TiCl3 based catalysts, the influence of catalyst composition, polymerization conditions, and monomer nature on Cp and Kp was studied.