Angiotensin II has significant physiological effects on tissues and organs throughout the body including vascular smooth muscle, adrenal cortex, kidney, and brain. Angiotensin II receptors are located on the plasma membrane of target cells to facilitate the rapid onset of angiotensin II. Three distinct subtypes of angiotensin II receptors have been identified: angiotensin II type-1 receptor, angiotensin type 2, and angiotensin type 4; and the relative proportion of each vary from tissue to tissue. The angiotensin II type-1 receptor subtype is expressed predominantly in vascular smooth muscle cells where activation by angiotensin II results in vasoconstriction, cell proliferation, fibrosis, and cellular hypertrophy. In contrast, angiotensin II type-2 receptor stimulation produces pharmacologic activities that are opposite to those that occur after angiotensin II type-1 receptor stimulation. The angiotensin II type-4 receptor has been reported to be expressed in the adrenals, brain, and myocardium, but its exact function remains unknown. It is not considered to play an important role in human pathogenesis.