The invention relates to a process for the preparation of a high activity procatalyst for the production of ethylene polymers. The process according to the present invention comprises the following steps:(a) contacting the inorganic support with an alkyl metal chloride which is soluble in non-polar hydrocarbon solvents, and has the formula(R.sub.n MeCl.sub.3-n).sub.m (1)wherein R is a C.sub.1 -C.sub.20 aklyl group, Me is a metal of group III(13) of the periodic table, n=1 or 2 and m=1 or 2, to give a first reaction product,(b) contacting said first reaction product with a compound or mixture containing hydrocarbyl and hydrocarbyl oxide linked to magnesium which is soluble in non-polar hydrocarbon solvents, to give a second reaction product, and(c) contacting said second reaction product with a titanium compound which contains chlorine, having the formulaCl.sub.x Ti(OR.sup.IV).sub.4-x (2)wherein R.sup.IV is a C.sub.2 -C.sub.20 hydrocarbyl group and x is 3 or 4, to give said procatalyst.