Dithioamine reducing agents useful for the reduction of disulfide bonds. The reducing agents of this invention are useful, for example, to reduce disulfide bonds, particularly in proteins, or to prevent the formation of disulfide bonds, particularly in proteins and other biological molecules. Reducing agents of this invention can be employed to regulate protein function in proteins in which a sulfhydryl group is associated with biological activity. Reducing agents of this invention can prevent inactivation of a given protein or enhance activation of a given protein or other biological molecule in vitro and/or in vivo. Reducing agents of this invention can prevent or reduce oxidation of cysteine residues in proteins and prevent the formation of reduced activity protein dimers (or other oligomers). Reducing agents of this invention are useful and suitable for application in a variety of biological applications, particularly as research and synthetic reagents.