The use of biomass as support for zirconocene catalysts in ethylene polymerization was studied. Cellulose, starch and chitosan were conveniently characterized. Many factors affecting the activity of the catalysts were examined. Parameters such as surface area were found to have no significant influence on the activity of the catalysts. The activity of the catalysts sharply increased with the degree of deacetylation in the chitosan supports. Using this support the highest activity in ethylene polymerization was obtained. The polymers obtained with the zirconocene supported on chitosan or cellulose pretreated with methylaluminoxane exhibited a higher molecular weight than those obtained with a homogeneous system. Polymer particles obtained with these supported metallocene catalysts showed a good replication of the original support particles.