The paper reports on the performance of highly dispersed synthetic magnesium silicate as a filler of the styrene-butadiene rubber (SBR). The magnesium silicate has been precipitated and characterized by determination of particle size distribution, electrokinetic potential, nitrogen adsorption/desorption isotherms and SEM observation. At the subsequent stage of the study its surface has been modified by silane coupling agents. The unmodified and silane-grafted magnesium silicate samples have been used as fillers of SBR of standard testing composition. The vulcanizates obtained with the fillers have been tested as to their physical and mechanical performance. The vulcanizates filled with synthetic magnesium silicate have been found to show much better mechanical parameters than unfilled rubber. Modification of the synthetic magnesium silicates with silane coupling agents has further improved the mechanical characteristics of the vulcanizates. (C) Koninklijke Brill NV, Leiden, 2010