Initiated from experimental results in the field of alkene oxidation in atmospheric chemistry, a novel production route for propylene oxide on an industrial scale is described. The proposed route represents a simple one-step process in the homogeneous gas phase under mild reaction conditions in the absence of a catalyst. The oxidizing agent is O-3. A selectivity to propylene oxide of up to 98% was achieved. This process is not afflicted with the production of coproducts, and only a negligible environmental burden is expected. Technical parameters, such as propylene conversion, selectivity, and formation rate of propylene oxide, are comparable to the corresponding data of the established, Ag-catalyzed ethylene oxide route. The homogeneous gas-phase route given is also applicable for the formation of ethylene oxide and butene oxides.