The copolymerization of ethylene with 1-hexene using Et[lnd](2)ZrCl2/MAO as catalyst was studied by multivariate methods. Three complete factorial designs were performed to study the influence of 1-hexene concentration, reaction temperature and [AI]/[Zr] ratio on catalytic activity, copolymer viscosity, crystallinity and melting point. Since the [AI]/[Zr] ratio has a small effect on the catalytic activity, a fourth design with 1-hexene and temperature was developed, giving higher catalytic activities. Temperature and 1-hexene concentration were the main effects found in the system. A second order effect arising from 1-hexene versus [AI]/[Zr] ratio was also detected. Polymer viscosity, crystallinity and melting points decreased with 1-hexene concentration. Viscosity decreased with temperature whereas crystallinity increased when the temperature was raised from 30 to 60 degrees C.