An ethylene/hexafluoropropylene elastomer composition which comprises an ethylene/hexafluoropropylene elastomer, a peroxide vulcanizing agent, and a vulcanization aid capable of generating an (un)saturated benzoyloxy radical. The vulcanization aid is, for example, p,p'−benzoylquinone dioxime. In the composition, the ethylene/hexafluoropropylene elastomer shows significantly improved suitability for vulcanization with the peroxide. Even when the composition contains a lowly reinforcing filler, no foaming is observed therein.
