Many vasoactive peptides induce vasodilation by acting via specific G-protein coupled receptors (GPCR). Drug development targets these receptors, as well as the enzymes that generate vasoactive peptides, as a means to gain control over this process as a potential treatment route of hypertension. Since its discovery by Yanagisawa in 1988, endothelin-1 (ET-1) has been consistently described as the most potent vasoconstrictor yet discovered. Specific antagonists to Endothelin A and B receptors are well-known and include BQ-123, BQ-610, and BQ-788. At the present time, urotensin (U II) is being considered the new endothelin by many due to its ultrapotent vasoconstrictive properties. Recently, Patacchini et al. introduced UrantideTM as a potent U II antagonist, the first reported of its kind. The importance of ET-1 and urotensin as cardiovascular and renal peptides in humans is well established, making these peptides and their antagonists highly important research tools.