Design changes in new model cars have resulted in higher under-the-hood temperatures. This has created a demand for rubber components that are more heat resistant. Since ethylene propylene terpolymer (EPDM) is a heat and weather resistant polymer being considered for many of these applications, this paper is presented to show the effect of various cure systems on heat resistance of EPDM compounds. The common sulfur cure system is useful to 300°F and the use of a sulfur donor system can extend that range to 350°F. Above 350°F a peroxide cure is shown to be necessary.