Graft polymerization of styrene into cellulose was investigated using Ceric ions redox systems as initiator. A mathematical model with the D-optimal design combined with the least squares method was applied to the system. The variables considered in the model are the reactant variables i.e. monomer and initiator concentrations and the processing variables i.e. reaction time, temperature and agitation rate. The optimal composition and processing conditions were determined using a three dimensional space analysis.