Since silica has strong filler-filler interactions and adsorbs polar materials, a silica-filled rubber compound has a poor dispersion of the filler and poor cure characteristics. Improvement of the properties of silica-filled styrene-butadiene rubber (SBR) compounds was studied using acrylonitrile-butadiene rubber (NBR). Viscosities and bound rubber contents of the compounds became lower by adding NBR to the compound. Cure characteristics of the compounds were improved by adding NBR. Physical properties such as modulus, tensile strength, heat buildup, abrasion, and crack resistance were also improved by adding NBR. Both wet traction and rolling resistance of the vulcanizates containing NBR were better than were those of the vulcanizate without NBR. The NBR effects in the silica-filled SBR compounds were compared with the carbon black-filled compounds.