The monovalent rhenium compounds ReBr(CO)(3)(3,3＇-dimethyl-2, 2＇-biquinoline) (I) and ReBr (CO)(5) (II) could be used as catalysts in styrene polymerization after activation with diphenylzinc (Ph2Zn) and methylaluminoxane (MAO). The catalytic activity shown by the I-Ph2Zn-MAO system was dependent on the molar ratio between the components and the temperature of polymerization. Non stereoregular polystyrene (PS) was obtained under all experimental conditions. The resulting PS gave multimodal GPC traces suggesting the presence of different species capable of polymerizing styrene, possibly species resulting from MAO alone, I-Ph2Zn and I-Ph2Zn-MAO systems.