Abstract: Ethene having a profitable .alpha.-olefin distribution and an .alpha.-olefin copolymer have been prepared with a process comprising reacting of at least the following components with each other:a) a procatalyst comprising a halogen compound of a transition metal in any of groups 4 to 8 of the periodic table of elements,b) a cocatalyst comprising an organohalogenous compound of a metal in group 2 or 3 of the periodic table of elements,c) ethene andd) one or more .alpha.-olefins copolymerizing with ethene, being characterised in that the organohalogenous compound of the metal in group 2 or 3 is prepared by reacting the organic compound of the metal in group 2 or 3 and a catalytically non-toxic halogen compound during copolymerization, or not earlier than 3 hours before copolymerization.