A summary of spectroscopic methods for structural and conformational elucidation of bioactive carbohydrates based on nuclear magnetic resonance (NMR) is described. The formation of carbohydrate-protein complexes is often the initial step of biological responses. Therefore, knowledge about the structural factors that stabilize the complex may be relevant and contribute to predict the structural/conformational requirements of new drugs acting as agonists. Two examples of medical significance in the cancer research field are discussed (1) conformational studies of glycoconjugates related to antitumour vaccines (2) conformational analysis of glycosaminoglycans and the interaction heparin-fibroblast growth factor (FGF).