Butadiene, styrene, cyclohexene, allyl acetate, methyl methacrylate, and allyl alcohol were epoxidized in a gas-phase reaction in the absence of a catalyst. The applied oxidizing agent is ozone. With exception of allyl alcohol (selectivity to glycidol: 58%), the selectivity to the corresponding epoxide ranged from 88 to 97%. For acrylonitrile, there was no measureable conversion.