Ethylenebis(eta(5)-fluorenyl) zirconium dichloride (1) and rac-dimethylsilylene bis(1-eta(5)-indenyl)zirconium dichloride (2) were activated with methylaluminoxane (MAO) to catalyze ethylene (E) propylene (P) copolymerizations. The former produces high MW copolymer at 20 degrees C rich in ethylene with reactivity ratio values of r(E) = 1.7 and r(p) < 0.01, whereas the latter produces lower MW random capolymers with r(E) = 1.32 and r(p) = 0.36. Ethylidene norbornene (ENB) complexes with 1/MAO but does not undergo insertion in the presence of E and P. In contrast, 2/MAO catalyzes terpolymerization incorporating 9-15 mol % of ENB with slightly lower MW and activity than the corresponding copolymerizations. In comparison, 1,4-hexadiene was incorporated by 2/MAO with much lower A and MW. Terpolymerizations were also conducted with vinylcyclohexene using both catalyst systems. The steric and electronic effects in these processes were discussed.