It is an exciting task to be the editor of the first monograph covering a new area of the biomedical sciences. Since the first report in 1980 by Robert Furchgott and colleagues (see Chapter 1) of the evidence of endothelium-dependent relaxation in isolated arteries, there are ever- increasing numbers of vascular physiologists and pharmacologists who are scraping away the endothelium to look into its role in cardiovascular con- trol. And the more one looks, the more one discovers. Not only is the list of substances that can induce endothelium-dependent relaxations im- pressively long, but...