Oligomers containing peroxy groups have been synthesized on the basis of epoxides and organic hydroperoxides. Dependence of reaction rates upon the ratio of starting materials, nature, quantity, concentration of ammonium salt catalysts, temperature and also nature of hydroperoxides have been investigated. Activation energies and effective rate constants of reactions between hydroperoxides and epoxy resins were calculated. The reaction proceeds by interfacial catalysis, and therefore with poor yields in solvents which are miscible with water (acetone and 1.4-dioxane) and with good yields in immiscible solvents (chloroform and toluene). Structures of the synthesized peroxy oligomers have been confirmed by IR-spectroscopy.