The natriuretic peptides are a family of structurally related peptides, products of at least three genes, which share a common, 17-membered, internal disulfide ring. Three major subtypes (A-, B-, and C-type natriuretic peptides) exist, and each is present in various tissues in multiple N- and C-terminally extended or shortened forms. The recent description of the C-type peptide CNP, the major brain-derived peptide, has suggested that original studies examining the endocrine actions of the natriuretic peptides using A-type (ANP) or B-type (BNP) isoforms might have underestimated some of the biopotency of the natriuretic peptides or even failed to detect the full spectrum of the family'S bioactivity. The identification of multiple, often species-specific, subtypes of the natriuretic peptides, together with the characterization of at least two classes of receptors for these hormones, indicates a variety of potential avenues for the development of therapeutic strategies for the use of these factors. Importantly, the description of protease inhibitors that prolong and enhance the actions of the natriuretic peptides in humans suggests potential for the recruitment of the natriuretic peptides in the treatment of endocrine as well as cardiovascular disease.