Abstract: Preparation of aralkyl monohydroperoxides comprising oxidizing an alkyl aromatic hydrocarbon in the liquid state by contacting the latter with oxygen or an oxygen containing gas at a temperature of about 40.degree. to 135.degree. C in the absence of any water, acid binding agent or reaction promoting agent, thereafter introducing the oxidate without cooling into a treatment zone maintained under conditions of pressure and vacuum whereby the unreacted hydrocarbon is evaporated, the heat required for the evaporation being solely the heat of formulation of the aralkyl monohydroperoxides.