A discussion with 8 refs. is given on the assignment of NMR spectra of complex systems, such as 1H or 13C spectra of macromols., which can be greatly facilitated by exploiting the phenomenon of coherence transfer. The topol. of the spin systems, i.e. the no. of spins and their connectivities through scalar or dipolar couplings, can be probed by suitably tailored sequences of radio-frequency pulses, and mapped by 2-dimensional Fourier transform methods. The interpretation of the resulting spectra can be facilitated by computer-aided pattern recognition methods. [on SciFinder (R)]