In　seismic　codes,　elastic　response　spectra　are　usually　defined　by　adopting　a　conventional　value　for　the　damping　ratio　equal　to　5%.　Damping　Reduction　Factors　(DRFs)　are　then　introduced　to　account　for　the　effect　of　damping　values　higher　than　the　nominal　5%.　In　this　framework,　the　main　aim　of　the　present　study　is　to　explore　a　new　definition　of　DRF.　The　concept　of　stochastic　response　spectrum　is　used　for　predicting　the　earthquake　response　of　a　structural　system　by　adopting　the　random　vibration　theory　for　nonstationary　processes.　The　peak　theory　is　finally　used　to　determine　the　DRF.