In addition to its role as an energy store, adipose tissue also acts as an endocrine organ, synthesizing and secreting hormones and cytokines. This review discusses angiotensin II (Ang-II), the biologically active component of the renin-angiotensin system (RAS). Evidence suggests that a functioning RAS is present in adipose tissue. Animal studies have demonstrated that modifying the amount of Ang-II in the body (eg, using RAS knockout/transgenic animal models or the pharmacological treatment of animal models to prevent the formation or action of Ang-II) directly influences body weight and adiposity. In humans, body fat is correlated with levels of angiotensinogen, a precursor of Ang-II. Thus, the treatment of obesity could be improved through the use of substances that interfere with Ang-II.