The ultimate properties of rubber products are strongly influenced by the size, size distribution, structure, surface area and surface selectivity of fillers. In this study, natural bauxite was coated with plasma polymer (polystyrene or polybutadiene) to modify surface properties. The coated and uncoated bauxites were tested as filler for SBR vulcanizates, using static and dynamic mechanical methods. The fracture surfaces of the vulcanizates were investigated by SEM. Plasma polymer modified bauxite loaded materials showed appreciable changes in hardness compared with samples loaded with uncoated bauxite. It was concluded that surface selectivity plays a more important role than surface area for bauxite in the SBR vulcanizates.