Frequency-switched single-transition cross-polarization (FS-ST-CP) provides a versatile-tool for selective coherence transfer in heteronuclear NMR of biomols. such as proteins and nucleic acids. This type of coherence transfer is spin-state-selective and can therefore benefit from the extension of the life-times of selected coherences due to partial cancellation of interfering relaxation mechanisms. The limits of the selectivity of the transfer are discussed by theory and illustrated by expt. The methods are particularly efficient to obtain quant. structural and dynamic information for selected residues in medium-sized nitrogen-15 or carbon-13 labeled macromols. [on SciFinder (R)]