A multi-purpose setup is presented for homo- and co-polymerizations of ethylene and I-hexene in slurry and gas phase. Polymerization experiments have been executed semi-batch with a heterogeneous metallocene catalyst under industrial conditions. During the gas phase polymerization, the monomer concentrations have been measured and controlled online. The activities for both monomers have been measured with flow meter technique. The polymerization kinetics presented have been measured in a very accurate and reproducible way in isothermal (within 0.2 degrees C) and isobaric mode (within 0.15 bar). The concentrations of monomer and co-monomer have been kept constant within 5% of the set point. The activity for ethylene was 50% higher in the presence of 1-hexene compared to a homo-polymerization. (c) 2006 Elsevier Ltd. All rights reserved.