Zirconocene dichloride and bis(n-butylcyclopentadienyl)zirconium dichloride are used as catalyst precursors for the heterogeneous polymerization of ethene. A methyl-substituted microgel as support material for heterogeneous cocatalysts on the basis of MAO is compared with different commercially available silica-supported cocatalysts. The catalyst performances and the properties of the obtained polyethenes show considerable differences.