With recent advances in methodology, it now appears that NMR can be used at an unprecedented level of sophistication to obtain new insights into the solution structure and dynamics of the antibody combining site, both free and in its complex with antigen. Most promising in this regard is the Fv fragment (molecular weight approximately 25 kD) which can be produced by genetic engineering in a form suitable for NMR studies. Isotopic labeling is required to make specific resonance assignments. NMR can also provide information on the conformational preferences of immunogenic peptides and can be used to probe the conformation and dynamics of peptides (appropriately labeled with 13C or 15N) bound to the Fab fragment (molecular weight approximately 50 kD) of antipeptide antibodies.