This article describes the effect of filler [obtained from bark of Acacia (Babool)] content and its particle size (ranging from 100 to 150 mu m and <50 mu m) on the properties of poly(vinyl chloride) (PVC) composites. Bark of the fast-growing species Acacia was used as powder for making PVC composites, which may find applications as a substitute to high-cost wood and to avoid deforestation. A two-roll mill was used for mixing varying amounts of bark flour with PVC formulation. Samples for testing were prepared by compression molding. Tensile strength and percentage of elongation at break decreased, whereas modulus increased with an increasing amount of bark flour. A significant increase in storage modulus (E') was observed upon incorporation of filler. Improvement in properties was significant in the presence of filler, having a particle size <50 mu m as compared to filler, having a particle size ranging from 100 to 150 mu m. Morphological characterization was conducted by using scanning electron microscopy. A uniform dispersion of filler was observed in PVC matrix. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 1309-1318, 2010