Hybrid composites of wood flour/kenaf fiber and polypropylene were prepared at a fixed fiber to plastic ratio of 40 : 60 and variable ratios of the two reinforcements namely 40: 0, 30:10, 20: 20,10: 30, and 0: 40 by weight. Polypropylene was used as the polymer matrix, and 40-80 mesh kenaf fiber and 60-100 mesh wood flour were used as the fiber and the particulate reinforcement, respectively. Maleic anhydride and dicumyl peroxide were also used as the coupling agent and initiator, respectively. Mixing process was carried out in an internal mixer at 180 degrees C at 60 rpm. ASTM D 638 Type I tensile specimens of the composites were produced by injection molding. Static tensile tests were performed to study the mechanical behavior of the hybrid composites. The hybrid effect on the elastic modulus of the composites was also investigated using the rule of hybrid mixtures and Halpin-Tsai equations. The relationship between experimental and predicted values was evaluated and accuracy estimation of the models was performed. The results indicated that while nonhybrid composites of kenaf fiber and wood flour exhibited the highest and lowest modulus values respectively, the moduli of hybrid composites were closely related to the fiber to particle ratio of the reinforcements. Rule of hybrid mixtures equation was able to predict the elastic modulus of the composites better than Halpin-Tsai equation. (C) 2007 Wiley Periodicals, Inc.