Star styrene-isoprene-butadiene rubber (SIBR) was synthesized with a new kind of star anionic initiator made from naphthalene lithium and an SnCl, coupled agent. The relationship between the structure and properties of star SIBR was studied. Star block styrene-isoprene-butadiene rubber (SB-SIBR), having low hysteresis, high road-hugging, and excellent mechanical properties, was closer to meeting the overall performance requirements of ideal tire-tread rubber according to a comparison of the morphology and various properties of SB-SIBR with those of star random SIBR and natural rubber/star styrene-butadiene rubber blends. (C) 2004 Wiley Periodicals, Inc.