A method for controlling a slurry polymerization for the preparation of polyethylene, where the polyethylene is formed in a polymerization reactor comprising a vapor section by contacting a Ziegler-type catalyst, ethylene, and either hydrogen or, as comonomer(s), one or more C3 to C10 alpha-olefins or hydrogen and one or more C3 to C10 alpha-olefins, wherein the ethylene partial pressure is maintained by adjusting the flow rate of the catalyst to the polymerization reactor and the hydrogen/ethylene and comonomer/ethylene partial pressure ratios are maintained by adjusting the flow rates of hydrogen and/or of the one or more comonomers to the polymerization reactor.