Angiotensin II is a multifunctional hormone that exerts its effects by interacting with cell surface receptors. Two major subtypes of receptors (AT1 and AT2) have been distinguished by pharmacological and molecular biological techniques. AT1 receptoxk have been further subdivided into AT~ A and AT~ B receptors. Several other isoforms have been found, notably in nonmammalian systems, but further information is necessary before definitive classification can be made. AT1 receptors mediate most known functions of angiotensin 11, while AT2 receptors may be important developmentally. The molecular, structural, and biochemical characteristics of these receptors have been described, as well as the factors that regulate their expression.'Ihis receptor system has been implicated in several cardiovascular diseases, including hypertension, restenosis after angioplasty, cardiac hypertrophy, heart failure, myocardial infarction, and ventricular remodeling. Structural analysis of AT receptors may provide the basis for the development of new therapeutic agents with enhanced specificity for the treatment of these diseases.