A multidimensional NMR methodol. for structure characterization of hydrocarbon-based polymers is described. This methodol. involves the use of selective 13C-labeling of the polymer and selective excitation of the resonances from the labeled site as if they were from a third NMR-active X-nucleus, to produce greatly simplified 3D-NMR spectra. The methodol. is illustrated on a sample of poly(ethylene-Bu acrylate-carbon monoxide) (polyEBC) prepd. from 1-13C-Bu acrylate (CH2:CH-13CO2-n-C4H9). The 1D 13C NMR spectrum of labeled polyEBC shows the expected enhancement of the ester-carbonyl resonances (~175 ppm), from selective 13C-labeling of B fragments, compared with the spectrum of similar, unlabeled polyEBC. The unique chem. shift correlations provide detailed structural information of complex polymers and macromols.