Homogeneous metallocene catalysts and several kinds of silica-supported metallocene catalysts were employed to investigate their catalytic behavior for styrene polymerization. Half metallocene directly supported on silica catalysts showed better performance than metallocene supported on silica treated with aluminum compounds with regard to syndiospecific styrene polymerization. The silica-supported metallocene catalysts had optimum conditions for Al/Ti mole ratio and polymerization temperature. Among these, the Cp*TiCl3/SiO2 catalyst showed fairly good catalytic activity and yielded enhanced properties of syncliotactic polystyrene, even at a relatively low (< 300) Al/Ti mole ratio in styrene polymerization. Active sites formed on SiO2 appear to be more thermally stable as compared with their homogeneous counterparts. (c) 2006 Wiley Periodicals, Inc.