The formation of disulfide bridges is often a crucial final stage in peptide synthesis. There is compelling evidence that the disulfide pattern can be critical in the folding and structural stabilization of many natural peptide and protein sequences, while the artificial introduction of disulfide bridges into natural or designed peptides may often improve biological activities/specificities and stabilities. This unit provides a highly selective, albeit state-of-the-art, menu of procedures that can be performed to establish intramolecular or intermolecular disulfide bridges in targets of varying complexities.