Silica-, nanoclay-, and carbon black (CB)filled ethylene-propylene-diene terpolymer (EPDM) mixtures were prepared and subsequently vulcanized. Rheological properties and cure characteristics of the mixtures and mechanical properties of vulcanizates were measured. Rheological property measurements indicated the storage modulus, toss modulus, and complex dynamic viscosity of silica-filled EPDM mixtures were much higher than those of CB-filled EPDM mixtures while tan delta values were lower. The optimum cure time of silica- and nanoclay-filled EPDM mixtures increased with filler loading, whereas the values for CB-filled mixtures slightly decreased with loading. The hardness, modulus, elongation at break, and tensile strength of all the vulcanizates increased with increasing filler loading. The elongation at break of CB-filled EPDM vulcanizates increased insignificantly with CB loading. Among the three fillers, the increase of the tensile strength and elongation at break was most significant for silica-filled EPDM vulcanizates. Remarkably, for 30 phr silica- filled EPDM vulcanizates, a tensile strength and elongation at break of 23.5 MPa and 1045% was achieved, respectively. (C) 2008 Wiley Periodicals, Inc.