Effects of heterogenization parameters on compositional and catalytic properties of Et(Ind)(2)ZrCl2 supported on silica modified with MAO were evaluated using data on metal loading, catalyst activity in ethylene-propylene copolymerization, and polymer properties. The supported catalysts were prepared according to a 2(3) factorial design for multivariate analysis. The parameters studied were: MAO concentration in impregnation, Et(Ind)(2)ZrCl2 concentration in grafting, and immobilization temperature for both metallocene and organoaluminum. The grafting solution was monitored by UV-VIS spectroscopy, while the resulting catalyst systems were characterized by inductively-coupled plasma-optical emission spectroscopy (ICP-OES), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS). At high statistical significance, both MAO and Et(Ind)(2)ZrCl2 concentrations during preparation affected the determination of the find Al/Zr ratio on silica, The catalyst systems were tested in ethylene-propylene copolymerizations using external MAO as cocatalyst. Relationships were observed between (i) catalyst activity and the binding energy of Zr 3d(5/2) electrons and (ii) Al/Zr ratio on silica and the average ethylene incorporation. The polymer samples presented narrow molecular weight distribution, but according to differential scanning calorimetry (DSC), and cross-fractionation chromatography (CFC) data, catalyst systems with given Al/Zr ratios might yield different crystallites, suggesting a plural distribution of chemical composition.