In this work three types of equipments were used, namely, rubber process analyzer (RPA 2000), Mooney viscometer, and dynamic mechanical thermal analyzer, to characterize natural rubber mixtures containing different amounts of regenerated celulose (Cel II) as filler. The RPA 2000 is a new dynamic rheological tester that can analyze raw polymers and masterbatches as well as rubber compounds before, during, and after cure. The Mooney viscometer is probably the most widely used method for measuring shearing viscosity of unvulcanized rubbers or rubber compositions. DMTA is used to assess filler-rubber interactions. In the present investigation, RPA tests on unvulcanized natural rubber and regenerated cellulose (Cel II) mixtures were carried out using strain and frequency sweeps, and the Mooney viscosities were determined using the relaxation accessory and the small rotor. DMTA data were taken at a fixed frequency and temperature sweep. The filler content was increased up to 30 phr. Compositions were prepared by cocoagulation of natural latex and cellulose xanthate mixtures. The results showed a good dispersion of the filler in the rubber matrix and its large influence on rheological and dynamic properties of the resulting compositions. (C) 2005 Wiley Periodicals, Inc.