H-1/C-13/(119)n triple-resonance 3D-NMR spectroscopy is used to characterize the tin-containing structures in the organotin polymer n-Bu3SnPBD (PBD = polybutadiene). Triple-resonance techniques, when used together with pulsed Geld gradient coherence selection, permit selective detection of the structure fragments near Sn-119 atom while removing intense signals of the PBD backbone from the spectrum. Three frequency dimensions provide enormous spectral dispersion, permitting the resolution of many signals that are not observable in 1D-NMR spectra. The simultaneous correlation of resonances from three nuclei provides a large amount of unambiguous atomic connectivity information. The capabilities of modern instruments are such that it is possible to perform these experiments without the benefit of isotopic labeling, despite the low concentration of chain ends and the low occurrence of fragments with H-1,C-13,and Sn-119 isotopes.