A panel of multidisciplinary experts describes in detail readily reproducible methods to investigate all aspects of the endothelin system from its synthesis and metabolism, to its function in health and disease. Theses methods use state-of-the-art molecular techniques to quantify the expression of mRNA for both endothelin receptors and the endothelin converting enzymes. They show how peptides, precursors, receptors, and synthetic enzymes can be localized and quantified in plasma, culture supernatants, tissue homogenate, and tissue sections using antibodies. Several in vivo protocols illustrate the role of the endothelin peptides in healthy human individuals and describe animal models that can be used to predict the therapeutic potential of cardiovascular drugs that manipulate endothelin synthesis or function.