Heterogeneous cyclopentadienylchromium catalysts were synthesized by adsorbing chromiumtrichloride CrCl3(THF)(3) on a cyclopentadienyl modified silica surface. The obtained catalysts and the homogeneous model compound, [CpCrMe(mu-Cl)](2) (Cp = eta(5)-C5H5), were tested in the polymerization of ethylene with the presence of the methylaluminoxane (MAO) cocatalyst. The heterogeneous catalyst showed a good activity toward ethylene but the main products were oligomers, mainly n-butene. The homogeneous catalyst was a better polymerization catalyst but it also produced oligomers. Heterogeneous catalysts were characterized with FTIR and C-13 and Si-29 CP MAS NMR.