In this research, the influence of adding a-cellulose powder to styrene-butadiene rubber (SBR) compounds was investigated. Physicomechanical properties of SBR-alpha-cellulose composites, including tensile strength, elongation, Young's modulus, tear strength, hardness, abrasion, resilience, and compression set, before and after ageing, were determined and analyzed. Young's modulus, hardness, and compression set increased and elongation and resilience decreased with increasing alpha-cellulose loading in the composites, whereas tensile strength, tear strength, and abrasion resistance initially increased at low alpha-cellulose concentration (5 phr), after which these properties decreased with increasing alpha-cellulose content. Lower loadings of alpha-cellulose (5 phr) showed better results than higher loadings, given that tensile strength, tear strength, and abrasion resistance increased at low a-cellulose concentration. Theoretical prediction of elastic moduli-is was carried out using rule of mixtures, Hashin, Kerner, and Halpin-Tsai equations. Calculated results show that these equations are not suitable for accurate prediction for the work carried out. However, these models can be used with confidence for the prediction of elastic modulus because experimental results are higher than the calculated values. (c) 2005 Wiley Periodicals, Inc.