The complete 1H and 13C NMR spectral assignments are described for the most prevalent patterns of sulfation and acetylation which can be found in polymeric heparin or can be obtained by standard chemical modifications. These include a number of novel structures containing unsubstituted or acetylated amino groups and the first complete NMR assignments of many of the other derivatives. Beef lung heparin was chosen as a model system and studies were carried out using conditions to control the influences on the chemical shift positions in heparin samples of divalent cations and variations in pH and temperature.