The effects of various polymerization conditions [GRAPHIC] such as cocatalyst concentration, pressure, temperature, and reaction time on ethylene homopolymerization over a SiO2-supported imido-vanadium/silyl-chromate (Cr-iV) bimetallic catalyst were systematically investigated. The monometallic silyl-chromate (S-2) and imido-vanadium (iV) catalyst were also employed for comparison. It was found that the S-2 catalyst produced a polymer with relatively low molecular weight, while the iV catalyst produced ultrahigh-molecular-weight polyethylene (UHMWPE). The bimetallic catalyst was capable of producing reactor blends, with bimodal molecular weight distribution (MWD) and a considerable amount of UHMWPE. Increasing and decreasing polymerization temperature both enhanced the high molecular weight part of the bimodal MWD while the position of the two peaks remained unchanged. The polymerization rates all showed first-order dependences with respect to ethylene pressure for the three catalysts. Ethylene pressure variations caused no changes in the MIND of polymers made by the three catalysts, indicating that transfer to the monomer is the main chain transfer mechanism.