In high-resoln. NMR spectra of scalar coupled spins in isotropic phase, it is possible to convert single- into triple-quantum coherences and vice versa by irradiating simultaneously at the frequencies of 3 chem. shifts. A triple resonance condition can be achieved by modulating a radiofrequency carrier by a product of 2 cosinusoidal audiowaves, chosen so that 3 of the 4 sidebands coincide with 3 selected chem. shifts. When used in conjunction with 2-dimensional Fourier transform spectroscopy, it is possible to obtain triple-quantum multiplets with very high resoln. within a limited time span. The linewidths can give an accurate measure of the relaxation rates of triple-quantum coherences. [on SciFinder (R)]