Radiation induced chain addition of allylbenzene to 1,4-dioxane has been studied by IR-, UV-, mass-, NMR- and ESR-spectrometry. Efficiency of the addition depends on the concentration of monomer and it has an optimum at C-monom<0.125M. Apparently, upper concentration limit of the reaction is caused by absorbed energy transfer on the molecule of monomer followed by energy deactivation. Radiation-chemical yields of the product are 12 and 31 molec./100 eV for 0.125M and 0.07M solution, respectively. The value of G(prod) is an evidence of chain character of the process.