An experimental setup and a kinetic study of the polymerization of propylene in liquid monomer with a highly active catalyst are presented. The purification system for monomer, the catalyst injection system, the temperature control system, and the polymerization procedures are described in detail. Further, reproducibility of the experiments is tested, the kinetics are described in the temperature range of 27 to 6 7 T , and the influence of prepolymerization in cold liquid propylene is investigated.