Because silica has strong filler-filler interactions, a silica-filled rubber compound shows a poor filler dispersion compared to a carbon black-filled one. Improvement of the filler dispersion in silica-filled styrene-butadiene rubber (SBR) compounds was studied using low molecular weight polybutadiene (liquid PBD) with the high content of 1,2-unit. By adding the liquid PBD to the silica-filled SBR compound, the filler dispersion and flow property are improved. The cure time and cure rate become faster as the 1,2-unit content of the liquid PBD increases for the compounds containing the liquid PBD. The crosslink density increases linearly with increase in the 1,2-unit content of the liquid PBD. (C) 2003 Wiley Periodicals, Inc.