A novel type of difference spectroscopy is proposed to improve two-dimensional exchange spectroscopy by reducing diagonal peaks which are often dominant in complex cases such as in 2-dimensional nuclear Overhauser effect spectra of biopolymers. The diagonal peaks appear with neg. algebraic sign and amplitudes equal to the sums of all cross-peaks appearing in a column or row of the 2-dimensional exchange spectra, agreeing with the elements of the corresponding exchange matrixes. The technique is applied to the indirect observation of the quadrupolar relaxation of D. [on SciFinder (R)]