Ethylene-propylene-diene monomer (EPDM) terpolymers were prepared using either vanadium (VOCl3/Al2Et3Cl3) or zirconocene (Et(Ind)(2)ZrCl2/MAO) catalyst systems. Residual metal contents in EPDM films were determined by Rutherford backscattering spectrometry. Metallocene catalyst systems exhibited a higher activity, producing EPDM with lower molecular weight and narrower molecular weight distribution. The highest activity guaranteed lower residual metal content (Zr/C = 10(-5)) than in the case of EPDM produced by VOCl3/Al2Et3Cl3 (V/C = 10(-4)). Subsequent steps of dissolution of the polymer and its reprecipitation were seen to reduce the metal contents in both metal systems. Concerning the cocatalyst retention, despite initial use of a very high amount of methylaluminoxane/metallocene (Al/Zr = 3000) in the reactor, only about 4% of this initial concentration remained in the polymer. On the other hand, in the case of vanadium-based catalyst, almost all Al present in the initial conditions (similar or equal to 8.3) remained in the polymer. In both cases, the residual AVM ratio was close to the value generally proposed for the generation/stabilization of the active species. In the case of vanadium systems, a test in the synthesis of ethylene propylene rubbers indicated that the absence of diene in the polymer structure leads to a reduction in the residual vanadium content, indicating that the diene double bond might be responsible for partially vanadium coordination.