Propylene was polymerized by binary zirconocenium catalysts derived from rac-ethylene-bis(1-eta5-indenyl)dimethylzirconium and cation forming agents (C6H5)3C+ (C6F5)4B- and (C6F5)3B. Polymerizations were also performed with the ternary systems of Et [Ind]2ZrCl2, Et3Al, and the cation forming agents. The catalyst systems, with the inert noncoordinating counter-ion, (C6F5)4B-, have much higher activity and stereoselectivity than the ones with the CH3B- (C6F5)3 counter-ion. Much less active still are catalysts having BF4- or (C6H5)4B- counter-ions. Similar but smaller effects of counter-ion structure on ethylene polymerization were observed.