A process for the production of cyclopentene free of C.sub.5 -diene impurities, which comprises metathetically reacting cis,cis-cyclodecadiene-(1,6) with a catalytic amount of a metathesis catalyst comprising a support material and an oxide of an element of Group VI A or VII A of the Periodic Table, at a reaction temperature of from 0.degree.C up to the temperature at which said catalyst decomposes, for a period of time sufficient to form said cyclopentene.