Silica supported (butylcyclopentadienyl)(2)ZrCl2/MAO catalysts were synthesized according to the "incipient wetness" method from a solution of metallocene in a liquid monomer. The monomer was allowed to polymerize yielding a catalyst containing polyhexene (PH), polystyrene (PS) or polyoctadiene (PO). One catalyst containing no polymer was also synthesized. The catalysts were used to polymerize ethene at 70 degrees C and 4 bar total pressure. The measured average activities were 5300 kg PE/(mol Zr.h) for (BuCp)(2)ZrCl2/MAO/PH/SiO2, 8600 kg PE/(mol Zr.h) for (BuCp)(2)ZrCl2/MAO/PS/SiO2, 3400 kg PE/(mol Zr.h) for (BuCp)(2)ZrCl2/MAO/PO/SiO2 and 5700 kg PE/(mol Zr.h) for (BuCp)(2)ZrCl2/MAO/SiO2. The polyhexene, polystyrene or polyoctadiene in the catalyst forms a protective layer around the active sites. Even after exposure to air for five hours these catalysts retain some polymerization activity.